#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull = unsigned long long;

#if 0
#define int ll
#define uint ull
#endif

/**
 * Problem: Barbar
 * URL: https://infoarena.ro/problema/barbar
 * TL: 200 ms
 * ML: 64 MB
 *
 * Good Luck!
*/

int dirl[4] = {-1, 1, 0, 0};
int dirc[4] = {0, 0, -1, 1};

void tc() {
    int n, m; cin >> n >> m;
    vector<vector<bool>> mat(n + 1, vector<bool>(m + 1));
    vector<vector<int>> minn(n + 1, vector<int>(m + 1, INT32_MAX));
    vector<vector<int>> maxx(n + 1, vector<int>(m + 1));
    queue<pair<int, int>> q;
    pair<int, int> ii, oo;
    for (int i = 1; i <= n; i ++) {
        for (int j = 1; j <= m; j ++) {
            char c; cin >> c;
            if (c == '*') mat[i][j] = true;
            else if (c == 'D') {
                minn[i][j] = 0;
                q.push({i, j});
            }
            else if (c == 'I') ii = {i, j};
            else if (c == 'O') oo = {i, j};
        }
    }

    while (!q.empty()) {
        auto [x, y] = q.front(); q.pop();

        for (int dir = 0; dir < 4; dir ++) {
            int xx = x + dirl[dir], yy = y + dirc[dir];

            if (1 <= xx && xx <= n && 1 <= yy && yy <= m && !mat[xx][yy] && minn[xx][yy] > minn[x][y] + 1) {
                minn[xx][yy] = minn[x][y] + 1;
                q.push({xx, yy});
            }
        }
    }

    maxx[ii.first][ii.second] = minn[ii.first][ii.second];
    q.push(ii);
    while (!q.empty()) {
        auto [x, y] = q.front(); q.pop();

        for (int dir = 0; dir < 4; dir ++) {
            int xx = x + dirl[dir], yy = y + dirc[dir];

            if (1 <= xx && xx <= n && 1 <= yy && yy <= m && !mat[xx][yy] && maxx[xx][yy] < min(maxx[x][y], minn[xx][yy])) {
                maxx[xx][yy] = min(maxx[x][y], minn[xx][yy]);
                q.push({xx, yy});
            }
        }
    }

    cout << maxx[oo.first][oo.second] << '\n';
}

#define MTC 0
#define FIO 1
#define FN "barbar"

signed main() {
#if FIO == 1 && !defined(LOCAL)
    (void)freopen(FN ".in", "r", stdin);
    (void)freopen(FN ".out", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#if MTC == 1
    signed tt; cin >> tt;
    while (tt --) tc();
#else
    tc();
#endif
    return 0;
}