#include <iostream>
#include <fstream>
#include <queue>
#include <climits>
using namespace std;
int a[1001][1001],startx,starty,endx,endy,n,m;
int b[1001][1001];
int di[]={1,0,-1,0};
int dj[]={0,1,0,-1};
queue <pair<int,int> > q;
ifstream f("barbar.in");
ofstream g("barbar.out");

bool check(int x,int y)
{
    if(x<1 || y <1 || x>n || y >m)
        return 0;
    return 1;
}

void bfs2(int startx,int starty,int endx,int endy)
{
    int i,j,inou,jnou;
    q.push(make_pair(startx,starty));
    while(!q.empty())
    {
        i=q.front().first;
        j=q.front().second;
        q.pop();
        //cout << i <<" " << j << "\n";
        for(int k=0;k<4;k++)
        {
            inou=i+di[k];
            jnou=j+dj[k];
            if(check(i,j) && a[inou][jnou]>=0)
            {
                if( b[inou][jnou]<b[i][j] && b[i][j]<=a[inou][jnou]){
                    b[inou][jnou]=b[i][j];
                    q.push(make_pair(inou,jnou));
                }else if(b[inou][jnou]==-1)
                {
                    b[inou][jnou]=a[inou][jnou];
                    q.push(make_pair(inou,jnou));
                }
            }
        }
    }
}

void bfs()
{
    int i,j,inou,jnou;
    while(!q.empty())
    {
        i=q.front().first;
        j=q.front().second;
        q.pop();
        for(int k=0;k<4;k++)
        {
            inou=di[k]+i;
            jnou=dj[k]+j;
            if(check(inou,jnou) && a[i][j]+1<a[inou][jnou])
            {
                a[inou][jnou]=a[i][j]+1;
                q.push(make_pair(inou,jnou));
            }
        }
    }

}

int main()
{
    f >> n >> m;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++){
            b[i][j]=-1;
            a[i][j]=INT_MAX;

        }
    char c;

    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
        {
            f >> c;
            if(c=='D')
            {
                a[i][j]=0;
                q.push(make_pair(i,j));
            }
            if(c=='*')
            {
                a[i][j]=-1;
            }

            if(c=='I')
            {
                startx=i;
                starty=j;
            }
            if(c=='O')
            {
                endx=i;
                endy=j;
            }
        }
    bfs();

    bfs2(startx,starty,endx,endy);




    g << b[endx][endy] << "\n";


    return 0;

}