#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};
int b[N][N];
int f[N][N];
struct c{ // coordonate
  int l, c;
};
void fiil(int n){

}
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;
    char x;
    for(int i = 1; i <= n; i++){
      for(int j = 1; j <= m; j++){
        in >> x;
        switch(x){
          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;
        }
      }
    }
    int st = 0, dr = n + m - 1;
    int rez = -1;
    while(st <= dr){
      int m = (st + dr) / 2;
        if(fiil(m)){
          rez = m;
          st = m + 1;
        }
        else
          dr = m - 1;
    }
    out << rez;
    return 0;
}