#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <algorithm>
#include <climits>

using namespace std;

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

int R, C, si, sj, fi, fj;
int mat[1005][1005], v[1005][1005];
int di[] = {-1, 1, 0, 0};
int dj[] = {0, 0, -1, 1};
queue<pair<pair<int, int>, int>> dgq;
queue<pair<int, int>> q;

void bfs_dragoni(){
    while (!dgq.empty()) {
        pair<pair<int, int>, int> curr = dgq.front();
        dgq.pop();

        for (int t = 0; t < 4; t++) {
            int ni = curr.first.first + di[t];
            int nj = curr.first.second + dj[t];

            if (ni >= 1 && ni <= R && nj >= 1 && nj <= C && mat[ni][nj] == INT_MAX) {
                mat[ni][nj] = curr.second + 1;
                dgq.push({{ni, nj}, curr.second + 1});
            }
        }
    }
}

bool bfs_paftenie(int k){
    if(mat[si][sj] < k) return false;

    for(int i = 1; i <= R; i++)
        for(int j = 1; j <= C; j++)
            v[i][j] = 0;

    while(!q.empty()) q.pop();

    q.push({si, sj});
    v[si][sj] = 1;

    while (!q.empty()) {
        pair<int, int> curr = q.front();
        q.pop();

        if(curr.first == fi && curr.second == fj) return true;

        for (int t = 0; t < 4; t++) {
            int ni = curr.first + di[t];
            int nj = curr.second + dj[t];

            if (ni >= 1 && ni <= R && nj >= 1 && nj <= C && mat[ni][nj] >= k && v[ni][nj] == 0){
                v[ni][nj] = 1;
                q.push({ni, nj});
            }
        }
    }
    return false;
}

int main(){
    f >> R >> C;

    for (int i = 1; i <= R; i++) {
        for (int j = 1; j <= C; j++) {
            char t;
            f >> t;
            if(t == '*') mat[i][j] = -2;
            else if(t == 'D'){ 
                mat[i][j] = 0; 
                dgq.push({{i, j}, 0}); 
            }
            else {
                mat[i][j] = INT_MAX;
                if(t == 'I'){ si = i; sj = j; }
                if(t == '0' || t == 'O'){ fi = i; fj = j; } 
            }
        }
    }

    bfs_dragoni();

    int l = 0, r = R + C, rasp = 0;
    
    while(l <= r){
        int m = l + (r - l)/2;
        if(bfs_paftenie(m)){
            rasp = m;
            l = m + 1;
        }
        else r = m - 1;
    }

    g << rasp;
    return 0;
}