#include <fstream>
#include <queue>
using namespace std;

ifstream in("barbar.in");
ofstream out("barbar.out");

int mat[1005][1005];
int r, c, nr_drag;

int dx[]={0,0,1,-1};
int dy[]={-1,1,0,0};

pair<int, int> coord_drag[1005], coord_start, coord_final;
queue<pair<int,int> > coada;

void captusire()
{
    for(int i=0; i<=r+1; i++)
        mat[i][0]=mat[i][c+1]=-1;

    for(int j=0; j<=c+1; j++)
        mat[0][j]=mat[r+1][j]=-1;
}

void alg_Lee(int x, int y)
{
    mat[x][y]=0;
    coada.push(make_pair(x,y));
    while(!coada.empty())
    {
        int okx=coada.front().first;
        int oky=coada.front().second;
        coada.pop();

        for(int i=0; i<4; i++)
        {
            int x2=okx+dx[i];
            int y2=oky+dy[i];

            if(mat[x2][y2]>mat[okx][oky]+1 || mat[x2][y2]==0)
            {
                mat[x2][y2]=mat[okx][oky]+1;
                coada.push(make_pair(x2,y2));
            }
        }
    }
}

int main()
{
    in>>r>>c;
    captusire();

    for(int i=1; i<=r; i++)
        for(int j=1; j<=c; j++)
        {
            char x;
            in>>x;

            if(x=='.')
                mat[i][j]=0;
            else if(x=='*')
                mat[i][j]=-1;
            else if(x=='D')
            {
                mat[i][j]=0;
                coord_drag[++nr_drag]=make_pair(i,j);
            }
            else if(x=='I')
            {
                mat[i][j]=0;
                coord_start=make_pair(i,j);
            }
            else if(x=='O')
            {
                mat[i][j]=0;
                coord_final=make_pair(i,j);
            }
        }

    for(int i=1; i<=nr_drag; i++)
        alg_Lee(coord_drag[i].first,coord_drag[i].second);

    out<<-1;

    in.close();
    out.close();
    return 0;
}