#include <bits/stdc++.h>

using namespace std;
const int N = 1002;
const int dl[] = {-1, 0, 1, 0};
const int dc[] = {0, -1, 0, 1};
char a[N][N];
int b[N][N];
int f[N][N];
struct c{ // coordonate
  int l, c;
};
int main()
{
    ifstream in("barbar.in");
    ofstream out("barbar.out");
    queue <c> q;
    queue <c> p;
    int n , m;
    in >> n >> m;
    int lf, cf;
    for(int i = 1; i <= n; i++){
      for(int j = 1; j <= m; j++){
        in >> a[i][j];
        switch(a[i][j]){
          case '.':
            b[i][j] = -1;
            break;
          case '*':
            b[i][j] = -2;
          break;
          case 'D':
            b[i][j] = 0;
            q.push((c){i,j});
          break;
          case 'I':
            b[i][j] = -1;
            p.push((c){i,j});
            break;
          case 'O':
            b[i][j] = -1;
            lf = i;
            cf = j;
            break;
        }
      }
    }
    while(!q.empty()){
      c x = q.front();
      q.pop();
      for(int k = 0; k < 4; k++){
        c y;
        y.l = x.l + dl[k];
        y.c = x.c + dc[k];
        if(b[y.l][y.c] == -1){
          b[y.l][y.c] = b[x.l][x.c] + 1;
          q.push((c){y.l,y.c});
        }
      }
    }
    f[p.front().l][p.front().c] = b[p.front().l][p.front().c];
    while(!p.empty()){
      c x = p.front();
      //f[x.l][x.c] = min(f[x.l][x.c], b[x.l][x.c]);
      p.pop();
      for(int k = 0; k < 4; k++){
        c y;
        y.l = x.l + dl[k];
        y.c = x.c + dc[k];
        if(b[y.l][y.c] > 0 && f[y.l][y.c] < f[x.l][x.c]){ //daca pot parcurge celula
          // nu ma intereseaza daca a mai fost parcursa ci daca este distanta minima este mai mare
          f[y.l][y.c] = min(f[x.l][x.c], b[y.l][y.c]);
          p.push((c){y.l,y.c});
        }
      }
    }
    /*
    for(int i = 1; i <= n; i++){
      for(int j = 1; j <= m; j++){
        out << f[i][j] << " ";
      }
      out << '\n';
    }*/
    if(f[lf][cf] == 0){
      out << -1;
    }
    else
      out << f[lf][cf];
    return 0;
}