#include <fstream>
#include <queue>
using namespace std;
ifstream f("barbar.in");
ofstream g("barbar.out");
int R,C;
int Matrix[1005][1005],DP[1005][1005],Counter[1005][1005];
int Aux[1005][1005];
bool Yes[1005][1005];
queue <int> Line;
queue <int> Col;
int X1,Y1,X2,Y2;
void Read()
{
    int i,j;
    int ident=1;
    f>>R>>C;
    for(i=1;i<=R;i++)
        for(j=1;j<=C;j++)
        {
            char value;
            f>>value;
            if(value=='*')
                Matrix[i][j]=-1;
            if(value=='I')
                X1=i,Y1=j;
            if(value=='O')
                X2=i,Y2=j;
            if(value=='D')
            {
                Line.push(i);
                Col.push(j);
                Yes[i][j]=1;
                Aux[i][j]=ident;
                ident++;
            }
        }
    for(i=0;i<=R+1;i++)
        Matrix[i][0]=Matrix[i][C+1]=-1;
    for(i=0;i<=C+1;i++)
        Matrix[0][i]=Matrix[R+1][i]=-1;
}
void Browse()
{
    while(!Line.empty())
    {
        int x=Line.front();
        int y=Col.front();
        Yes[x][y]=0;
        Line.pop();
        Col.pop();
        if(Aux[x+1][y]==0 && Matrix[x+1][y]!=-1)
        {
            Matrix[x+1][y]=Matrix[x][y]+1;
            Line.push(x+1);
            Col.push(y);
            Yes[x+1][y]=1;
            Aux[x+1][y]=Aux[x][y];
        }
        else
        {
            if(Matrix[x+1][y]!=-1)
            {
                if(Matrix[x+1][y]>Matrix[x][y]+1)
                {
                    Matrix[x+1][y]=Matrix[x][y]+1;
                    if(Yes[x+1][y]==0)
                    {
                        Line.push(x+1);
                        Col.push(y);
                        Yes[x+1][y]=1;
                    }
                }
            }
        }
        if(Aux[x-1][y]==0 && Matrix[x-1][y]!=-1)
        {
            Matrix[x-1][y]=Matrix[x][y]+1;
            Line.push(x-1);
            Col.push(y);
            Yes[x-1][y]=1;
            Aux[x-1][y]=Aux[x][y];
        }
        else
        {
            if(Matrix[x-1][y]!=-1)
            {
                if(Matrix[x-1][y]>Matrix[x][y]+1)
                {
                    Matrix[x-1][y]=Matrix[x][y]+1;
                    if(Yes[x-1][y]==0)
                    {
                        Line.push(x-1);
                        Col.push(y);
                        Yes[x-1][y]=1;
                    }
                }
            }
        }
        if(Aux[x][y-1]==0 && Matrix[x][y-1]!=-1)
        {
            Matrix[x][y-1]=Matrix[x][y]+1;
            Line.push(x);
            Col.push(y-1);
            Yes[x][y-1]=1;
            Aux[x][y-1]=Aux[x][y];
        }
        else
        {
            if(Matrix[x][y-1]!=-1)
            {
                if(Matrix[x][y-1]>Matrix[x][y]+1)
                {
                    Matrix[x][y-1]=Matrix[x][y]+1;
                    if(Yes[x][y-1]==0)
                    {
                        Line.push(x);
                        Col.push(y-1);
                        Yes[x][y-1]=1;
                    }
                }
            }
        }
        if(Aux[x][y+1]==0 && Matrix[x][y+1]!=-1)
        {
            Matrix[x][y+1]=Matrix[x][y]+1;
            Line.push(x);
            Col.push(y+1);
            Yes[x][y+1]=1;
            Aux[x][y+1]=Aux[x][y];
        }
        else
        {
            if(Matrix[x][y+1]!=-1)
            {
                if(Matrix[x][y+1]>Matrix[x][y]+1)
                {
                    Matrix[x][y+1]=Matrix[x][y]+1;
                    if(Yes[x][y+1]==0)
                    {
                        Line.push(x);
                        Col.push(y+1);
                        Yes[x][y+1]=1;
                    }
                }
            }
        }
    }
}
void Solve()
{
    Line.push(X1);
    Col.push(Y1);
    DP[X1][Y1]=Matrix[X1][Y1];
    while(!Line.empty())
    {
        int x=Line.front();
        int y=Col.front();
        Line.pop();
        Col.pop();
        Yes[x][y]=0;
        if(Matrix[x+1][y]!=-1)
        {
            if(DP[x+1][y]<DP[x][y])
            {
                DP[x+1][y]=DP[x][y];
                if(DP[x+1][y]>Matrix[x+1][y])
                {
                    Counter[x+1][y]++;
                    DP[x+1][y]=Matrix[x+1][y];
                    if(Counter[x+1][y]<=1 && Yes[x+1][y]==0)
                    {
                        Line.push(x+1);
                        Col.push(y);
                        Yes[x+1][y]=1;
                    }
                }
                else
                {
                    if(Yes[x+1][y]==0)
                    {
                        Line.push(x+1);
                        Col.push(y);
                        Yes[x+1][y]=1;
                    }
                }
            }
        }
        if(Matrix[x-1][y]!=-1)
        {
            if(DP[x-1][y]<DP[x][y])
            {
                DP[x-1][y]=DP[x][y];
                if(DP[x-1][y]>Matrix[x-1][y])
                {
                    Counter[x-1][y]++;
                    DP[x-1][y]=Matrix[x-1][y];
                    if(Counter[x-1][y]<=1 && Yes[x-1][y]==0)
                    {
                        Line.push(x-1);
                        Col.push(y);
                        Yes[x-1][y]=1;
                    }
                }
                else
                {
                    if(Yes[x-1][y]==0)
                    {
                        Line.push(x-1);
                        Col.push(y);
                        Yes[x-1][y]=1;
                    }
                }
            }
        }
        if(Matrix[x][y-1]!=-1)
        {
            if(DP[x][y-1]<DP[x][y])
            {
                DP[x][y-1]=DP[x][y];
                if(DP[x][y-1]>Matrix[x][y-1])
                {
                    Counter[x][y-1]++;
                    DP[x][y-1]=Matrix[x][y-1];
                    if(Counter[x][y-1]<=1 && Yes[x][y-1]==0)
                    {
                        Line.push(x);
                        Col.push(y-1);
                        Yes[x][y-1]=1;
                    }
                }
                else
                {
                    if(Yes[x][y-1]==0)
                    {
                        Line.push(x);
                        Col.push(y-1);
                        Yes[x][y-1]=1;
                    }
                }
            }
        }
        if(Matrix[x][y+1]!=-1)
        {
            if(DP[x][y+1]<DP[x][y])
            {
                DP[x][y+1]=DP[x][y];
                if(DP[x][y+1]>Matrix[x][y+1])
                {
                    Counter[x][y+1]++;
                    DP[x][y+1]=Matrix[x][y+1];
                    if(Counter[x][y+1]<=1 && Yes[x][y+1]==0)
                    {
                        Line.push(x);
                        Col.push(y+1);
                        Yes[x][y+1]=1;
                    }
                }
                else
                {
                    if(Yes[x][y+1]==0)
                    {
                        Line.push(x);
                        Col.push(y+1);
                        Yes[x][y+1]=1;
                    }
                }
            }
        }
    }
    if(DP[X2][Y2]==0)
    {
        g<<-1<<"\n";
        return;
    }
    else
        g<<DP[X2][Y2]<<"\n";
}
int main()
{
    Read();
    Browse();
    Solve();
    return 0;
}