#include <algorithm>
#include <fstream>
#include <queue>

#define MaxN 1005

using namespace std;

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

int R, C, dist[MaxN][MaxN];
int vizitat[MaxN][MaxN], vizibil[MaxN][MaxN], trebuie_viz[MaxN][MaxN];
int XStart, YStart, XFinish, YFinish;
char mat[MaxN][MaxN];
vector<pair<int, int>> celule;
queue<pair<int, int>> q;

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

bool isInside(int x, int y) { return x >= 1 && x <= R && y >= 1 && y <= C; }

void BFS() {
    while (!q.empty()) {
        celule.push_back(
            q.front()); // contine celulele sortate crescator dupa distanta
        int x = q.front().first;
        int y = q.front().second;
        q.pop();

        for (int i = 0; i < 4; i++) {
            int new_x = x + dx[i];
            int new_y = y + dy[i];

            if (!isInside(new_x, new_y) || mat[new_x][new_y] == '*')
                continue;

            if (dist[new_x][new_y] == -1) {
                dist[new_x][new_y] = dist[x][y] + 1;
                q.push({new_x, new_y});
            }
        }
    }
    reverse(celule.begin(), celule.end());
}

void vizitare(int x, int y) {
    vizitat[x][y] = 1;
    trebuie_viz[x][y] = 0;

    for (int i = 0; i < 4; i++) {
        int new_x = x + dx[i];
        int new_y = y + dy[i];
        if (isInside(new_x, new_y) && vizitat[new_x][new_y] == 0) {
            trebuie_viz[new_x][new_y] = 1;
            if (vizibil[new_x][new_y] == 1) {
                vizitare(new_x, new_y);
            }
        }
    }
}

int main() {
    fin >> R >> C;

    for (int i = 1; i <= R; i++) {
        fin >> (mat[i] + 1);
        for (int j = 1; j <= C; j++) {
            dist[i][j] = -1; // celula e nevizitata
            if (mat[i][j] == 'I') {
                XStart = i;
                YStart = j;
            } else if (mat[i][j] == 'O') {
                XFinish = i;
                YFinish = j;
            } else if (mat[i][j] == 'D') {
                q.push({i, j});
                dist[i][j] = 0; // 0 daca e dragon
            }
        }
    }

    BFS();

    trebuie_viz[XStart][YStart] = 1;
    for (auto &celula : celule) {
        int x = celula.first;
        int y = celula.second;
        vizibil[x][y] = 1;

        if (trebuie_viz[x][y]) {
            vizitare(x, y);
        }

        if (vizitat[XFinish][YFinish]) {
            fout << dist[x][y] << endl;
            return 0;
        }
    }

    fout << -1 << endl;

    return 0;
}