// https://infoarena.ro/problema/barbar
#include <bits/stdc++.h>
using namespace std;
#define endl '\n'

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

const pair<int,int> dir[4]={{1, 0}, {-1, 0}, {0, 1}, {0, -1}};

int main() {
  int n, m;
  fin>>n>>m;

  queue<pair<int,int>> dq;
  vector<vector<char>> t(n+2, vector<char>(m+2));
  vector<vector<int>> dep(n+2, vector<int>(m+2)), mini(n+2, vector<int>(m+2));
  vector<vector<bool>> vis(n+2, vector<bool>(m+2,true));
  int pl, pc, il, ic;
  for (int i=1; i<=n; ++i) {
    for (int j=1; j<=m; ++j) {
      fin>>t[i][j];
      vis[i][j] = false;
      if (t[i][j]=='D') dq.push({i, j});
      else if (t[i][j]=='I') pl=i, pc=j;
      else if (t[i][j]=='O') il=i, ic=j;
    }
  }

  while (!dq.empty()) {
    int x=dq.front().first, y=dq.front().second;
    dq.pop();
    vis[x][y] = true;

    for (auto d:dir) {
      int l=x+d.first, c=y+d.second;
      if (!vis[l][c]) {
        dep[l][c] = dep[x][y]+1;
        dq.push({l, c});
      }
    }
  }

  bool ok=false;
  priority_queue<pair<int,int>> pq;
  pq.push({pl, pc});
  mini[pl][pc] = dep[pl][pc];
  while (!pq.empty()) {
    int x=pq.top().first, y=pq.top().second;
    pq.pop();
    vis[x][y] = true;
    
    if (x==il && y==ic) {
      ok = true;
      continue;
    }

    for (auto d:dir) {
      int l=x+d.first, c=y+d.second;
      if ((t[l][c]=='.' || t[l][c]=='O') && mini[l][c]<min(dep[l][c], mini[x][y])) {
        mini[l][c] = min(dep[l][c], mini[x][y]);
        pq.push({l, c});
      }
    }
  }

  fout<<(ok?mini[il][ic]:-1);
}