#include <bits/stdc++.h>
#define cin fin
#define cout fout
using namespace std;
ifstream cin("barbar.in");
ofstream cout("barbar.out");
int n, m, D[1002][1002], Min[1002][1002];
char M[1002][1002];

int dx[] = {0, 0, 1, -1};
int dy[] = {-1, 1, 0, 0};

queue <pair<int, int> > Q;

bool inMatrix(int x, int y) {
    return x > 0 && x <= n && y > 0 && y <= m;
}

void LeeDistDrag() {
    while(!Q.empty()) {
        int l = Q.front().first;
        int c = Q.front().second;
        Q.pop();
        for(int k = 0; k < 4; ++k) {
            int x = l + dx[k];
            int y = c + dy[k];
            if(inMatrix(x, y) && M[x][y] != '*' && D[x][y] == 2e9) {
                D[x][y] = D[l][c] + 1;
                Q.push({x, y});
            }
        }
    }
}

void lee() {
    while(!Q.empty()) {
        int l = Q.front().first;
        int c = Q.front().second;
        Q.pop();
        for(int k = 0; k < 4; ++k) {
            int x = l + dx[k];
            int y = c + dy[k];
            if(inMatrix(x, y) && M[x][y] != '*' && Min[x][y] < min(Min[l][c], D[x][y])) {
                Min[x][y] = min(Min[l][c], D[x][y]);
                Q.push({x, y});
            }
        }
    }
}

int main()
{
    cin >> n >> m;
    int x, y, xx, yy;
    for(int i = 1; i <= n; ++i) {
        cin >> (M[i] + 1);
        for(int j = 1; j <= m; ++j) {
            D[i][j] = 2e9;
            Min[i][j] = -1;
            if(M[i][j] == 'D') {
                D[i][j] = 0;
                Q.push({i, j});
            }
            else if(M[i][j] == 'I') {
                x = i;
                y = j;
            }
            else if(M[i][j] == 'O') {
                xx = i;
                yy = j;
            }
        }
    }
    LeeDistDrag();
    Min[x][y] = D[x][y];
    Q.push({x, y});
    lee();
    cout << Min[xx][yy];
    return 0;
}