//ALEX ENACHE

#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <unordered_map>
#include <time.h>
#include <iomanip>
#include <deque>
#include <math.h>
#include <assert.h>
#include <stack>
#include <bitset>
#include <random>

using namespace std;

//-----------------------------------------------------------------

#include <fstream>

//ifstream cin("input"); ofstream cout("output");
ifstream cin("barbar.in"); ofstream cout("barbar.out");

const int inf = 1e9;
const int MAXN = 1010;

queue < pair < int , int> > q;
int obst[MAXN][MAXN];
int dist[MAXN][MAXN];
int used[MAXN][MAXN];

int dirx[] = { 0 , 0 , 1 , -1 };
int diry[] = { 1 , -1 , 0 , 0 };

int main() {

	int n , m;
	cin >> n >> m;

	char c;
	pair < int, int > start, end;

	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			dist[i][j] = inf;
			cin >> c;
			if (c == '*') {
				obst[i][j] = 1;
			}
			if (c == 'D') {
				q.push({ i , j });
				dist[i][j] = 0;
			}
			if (c == 'I') {
				start = { i , j };
			}
			if (c == 'O') {
				end = { i , j };
			}
		}
	}

	while (!q.empty()) {
		pair < int, int > now = q.front();
		q.pop();
		for (int i = 0; i < 4; i++) {
			int x = now.first + dirx[i];
			int y = now.second + diry[i];

			if (x < 1 || x > n || y < 1 || y > m) {
				continue;
			}
			if (obst[x][y]) {
				continue;
			}
			if (dist[x][y] <= dist[now.first][now.second] + 1) {
				continue;
			}
			dist[x][y] = dist[now.first][now.second] + 1;
			q.push({ x , y });
		}
	}

	int st = 0, dr = n * m;
	int ans = 0;

	while (st <= dr) {
		int mij = st + dr;
		mij /= 2;

		used[start.first][start.second] = 1;
		q.push(start);

		while (!q.empty()) {
			pair < int, int > now = q.front();
			q.pop();
			for (int i = 0; i < 4; i++) {
				int x = now.first + dirx[i];
				int y = now.second + diry[i];

				if (x < 1 || x > n || y < 1 || y > m) {
					continue;
				}
				if (obst[x][y]) {
					continue;
				}
				if (dist[x][y] < mij) {
					continue;
				}
				if (used[x][y]) {
					continue;
				}
				used[x][y] = 1;
				q.push({ x , y });
			}
		}

		if (used[end.first][end.second]) {
			st = mij + 1;
			ans = mij;
		}
		else {
			dr = mij - 1;
		}

		for (int i = 1; i <= n; i++) {
			for (int j = 1; j <= m; j++) {
				used[i][j] = 0;
			}
		}
	}

	cout << ans;

	return 0;
}