#include <bits/stdc++.h>
#define ll long long
#define sz(x) (int)(x).size()
#define debug(v,n) for (int i = 1; i <= (n); ++i) cout << v[i] << " ";
#define next cout << '\n'
using namespace std;

const int N = 1005;
int n, m, ans;
char mt[N][N];
int dp[N][N];
bool in[N][N];
pair<int, int> x, y, dragon;

int dl[4] = {0, 1, 0, -1};
int dc[4] = {1, 0, -1, 0};

struct cmp {
    bool operator()(pair<int,int> a, pair<int,int> b) {
        return dp[a.first][a.second] < dp[b.first][b.second];
    }
};
priority_queue<pair<int,int>, vector<pair<int,int>>, cmp> q;

void bfs(int i, int j) {
    q.push({i, j});

    while(!q.empty()) {
        i = q.top().first;
        j = q.top().second;
        q.pop();

        for (int d = 0; d < 4; ++d) {
            if(mt[i + dl[d]][j + dc[d]] == '.') {
                dp[i + dl[d]][j + dc[d]] = min(dp[i][j], dp[i + dl[d]][j + dc[d]]);
                if(in[i + dl[d]][j + dc[d]] == false) {
                    q.push({i + dl[d], j + dc[d]});
                    in[i + dl[d]][j + dc[d]] = true;
                }
            }
        }
    }
}

int main() {
    //ifstream fin("date.in.txt");
    ifstream fin("barbar.in");
    ofstream fout("barbar.out");
    fin >> n >> m;
    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= m; ++j) {
            fin >> mt[i][j];
            if(mt[i][j] == 'D')
                dragon = {i, j};
            else if(mt[i][j] == 'I') {
                x = {i, j};
                mt[i][j] = '.';
            }
            else if(mt[i][j] == 'O') {
                y = {i, j};
                mt[i][j] = '.';
            }
            dp[i][j] = INT_MAX;
        }
    }

    queue<pair<int,int>> coada;
    coada.push({dragon.first, dragon.second});
    dp[dragon.first][dragon.second] = 0;
    while(!coada.empty()) {
        int i = coada.front().first;
        int j = coada.front().second;
        coada.pop();
        in[i][j] = false;

        for (int d = 0; d < 4; ++d) {
            if(mt[i + dl[d]][j + dc[d]] == 'D') {
                dp[i + dl[d]][j + dc[d]] = 0;
                if(in[i + dl[d]][j + dc[d]] == false) {
                    coada.push({i + dl[d], j + dc[d]});
                    in[i + dl[d]][j + dc[d]] = true;
                }
            }
            else if(dp[i][j] + 1 < dp[i + dl[d]][j + dc[d]] && mt[i + dl[d]][j + dc[d]] == '.') {
                dp[i + dl[d]][j + dc[d]] = dp[i][j] + 1;
                if(in[i + dl[d]][j + dc[d]] == false) {
                    coada.push({i + dl[d], j + dc[d]});
                    in[i + dl[d]][j + dc[d]] = true;
                }
            }
        }
    }
    /*for (int i = 1; i <= n; ++i){
        for (int j =1; j <= m; ++j) {
            cout << dp[i][j] << " ";
        }
        cout << '\n';
    }*/
    bfs(x.first, x.second);
    /*cout << '\n';
    for (int i = 1; i <= n; ++i){
        for (int j =1; j <= m; ++j) {
            cout << dp[i][j] << " ";
        }
        cout << '\n';
    }*/
    fout << dp[y.first][y.second];
    return 0;
}