#include <bits/stdc++.h>

//std::ifstream fin ("input.txt");
//std::ofstream fout ("output.txt");

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

int dp[1005][1005];
int dragon[1005][1005];
bool a[1005][1005];

struct str{
    int cost, i, j;
    str(int cost, int i, int j)
        : cost(cost), i(i), j(j)
    {
    }
};

struct compare {
    bool operator() (str const& p1, str const& p2){
        return p1.cost > p2.cost;
    }
};

std::deque < std::pair < int, int > > dq;
std::priority_queue <  str, std::vector < str >, compare > pq;

void BFS_dragons (int n, int m){
    int di[4] = {-1, 0, 1, 0};
    int dj[4] = {0, -1, 0, 1};
    int ii, jj, i, j;
    while (!dq.empty()){
        i = dq.front().first;
        j = dq.front().second;
        dq.pop_front();
        for (int k=0; k<4; k++){
            ii = i + di[k];
            jj = j + dj[k];
            if (0 <= ii and ii < n)
            if (0 <= jj and jj < m)
            if (a[ii][jj] == 0)
            if (dragon[ii][jj] > dragon[i][j] + 1){
                dragon[ii][jj] = dragon[i][j] + 1;
                dq.push_back ({ii, jj});
            }
        }
    }
}

void BFS_player (int n, int m){
    int di[4] = {-1, 0, 1, 0};
    int dj[4] = {0, -1, 0, 1};
    int i, j, ii, jj;
    while (!pq.empty()){
        i = pq.top().i;
        j = pq.top().j;
        pq.pop();
        for (int k=0; k<4; k++){
            ii = i + di[k];
            jj = j + dj[k];
            if (0 <= ii and ii < n)
            if (0 <= jj and jj < m)
            if (a[ii][jj] == 0)
            if (dp[ii][jj] < std::min (dp[i][j], dragon[ii][jj])){
                dp[ii][jj] = std::min (dp[i][j], dragon[ii][jj]);
                pq.push ({dp[ii][jj], ii, jj});
            }
        }
    }
}


int main()
{
    int n, m, i, j;
    int sx, sy, fx, fy;
    char chr;
    fin >> n >> m;

    std::string s;
    for (i=0; i<n; i++){
        fin >> s;
        for (j=0; j<m; j++){
            dragon[i][j] = INT_MAX;
            dp[i][j] = -1;
            chr  = s[j];
            if (chr == '.'){
                a[i][j] = 0;
                continue;
            }

            if (chr == '*'){
                a[i][j] = 1;
                continue;
            }

            if (chr == 'I'){
                a[i][j] = 0;
                sx = i;
                sy = j;
                continue;
            }
            if (chr == 'O'){
                a[i][j] = 0;
                fx = i;
                fy = j;
                continue;
            }
            if (chr == 'D'){
                dq.push_back ({i, j});
                a[i][j] = 0;
                dragon[i][j] = 0;
                continue;
            }
        }
    }


    BFS_dragons (n, m);

    /*
    for (i=0; i<n; i++, fout << '\n')
        for (j=0; j<m; j++)
        fout << dragon[i][j] << ' ';
        */

    dp[sx][sy] = dragon[sx][sy];
    pq.push ({dp[sx][sy], sx, sy});
    BFS_player (n, m);

    /*
    for (i=0; i<n; i++, fout << '\n')
        for (j=0; j<m; j++)
        fout << dp[i][j] << ' ';
        */

    fout << dp[fx][fy] << '\n';

    return 0;
}