#include <iostream>
#include <stdio.h>
using namespace std;

struct Coord {
    int x;
    int y;
    Coord () {
        x = 0;
        y = 0;
    }

    Coord (int inX, int inY) {
        x = inX;
        y = inY;
    }
};

int Height, Width;
char Board [1000][1000];

Coord Dragons[1000000];
Coord Exit;
Coord Entry;
int DragonTop;
bool valid;

void Draw (Coord Center, int Radius) {
    for (int i = 0; i < Radius; i++) //TOP RIGHT
        if (Center.x + i < Width && Center.y + Radius - i < Height)
            if (Board [Center.x + i][Center.y + Radius - i] != '*')
                Board [Center.x + i][Center.y + Radius - i] = 'X';

    for (int i = 0; i < Radius; i++) //BOTTOM RIGHT
        if (Center.x + Radius - i < Width && Center.y - i >= 0)
            if (Board [Center.x + Radius - i][Center.y - i] != '*')
                Board [Center.x + Radius - i][Center.y - i] = 'X';

    for (int i = 0; i < Radius; i++) //BOTTOM LEFT
        if (Center.x - i >= 0 && Center.y - Radius + i >= 0)
            if (Board [Center.x - i][Center.y - Radius + i] != '*')
                Board [Center.x - i][Center.y - Radius + i] = 'X';

    for (int i = 0; i < Radius; i++) //TOP LEFT
        if (Center.x - Radius + i >= 0 && Center.y + i < Height)
            if (Board [Center.x - Radius + i][Center.y + i] != '*')
                Board [Center.x - Radius + i][Center.y + i] = 'X';
}

void ClearBoard() {
    for (int i = 0; i < Height; i++)
        for (int k = 0; k < Width; k++)
            if (Board [i][k] == 'X' || Board[i][k] == 'P')
                Board[i][k] = '.';
}

void ShowBorder() {
    for (int i = 0; i < Height; i++) {
        for (int k = 0; k < Width; k++)
            cout << Board[i][k] << " ";
        cout << '\n';
    }
}

void Lee(Coord pos) {
    if (!valid) {
        if (pos.x == Exit.x && pos.y == Exit.y) {
            valid = true;
            return;
        }

        if (Board [pos.x][pos.y] == '.' || Board [pos.x][pos.y] == 'I') {
            Board [pos.x][pos.y] = 'P';

            if (pos.x + 1 < Width) {
                char cobai = Board[pos.x + 1][pos.y];
                if (cobai != 'P' && cobai != 'X' && cobai != '*')
                    Lee (Coord(pos.x + 1, pos.y));
            }

            if (pos.x - 1 >= 0) {
                char cobai = Board[pos.x - 1][pos.y];
                if (cobai != 'P' && cobai != 'X' && cobai != '*')
                    Lee (Coord(pos.x - 1, pos.y));
            }

            if (pos.y + 1 < Height) {
                char cobai = Board[pos.x][pos.y + 1];
                if (cobai != 'P' && cobai != 'X' && cobai != '*')
                    Lee (Coord(pos.x, pos.y + 1));
            }

            if (pos.y - 1 >= 0) {
                char cobai = Board[pos.x][pos.y - 1];
                if (cobai != 'P' && cobai != 'X' && cobai != '*')
                    Lee (Coord(pos.x, pos.y - 1));
            }
        }
    }
}

int main() {
    freopen("barbar.in", "r", stdin);
    freopen("barbar.out", "w", stdout);

    cin >> Height >> Width;
    for (int i = 0; i < Height; i++)
        for (int k = 0; k < Width; k++) {
            cin >> Board[i][k];
            if (Board[i][k] == 'D') {
                Dragons[DragonTop++] = Coord(i, k);
                Board[i][k] = 'X';
            }

            if (Board[i][k] == 'I')
                Entry = Coord (i, k);
            if (Board[i][k] == 'O')
                Exit = Coord (i, k);
        }

    int CurrentLevel = 2500;
    int lvl = 0;

    for (int i = 1; i <= CurrentLevel; i++) {
        valid = false;
        for (int k = 0; k < DragonTop; k++)
            Draw (Dragons[k], i);
        Lee(Entry);
        if (valid)
            lvl = i;

        //ShowBorder();
        //cout << '\n';
        //cout << '\n';
        ClearBoard();
    }
    cout << lvl + 1;
    return 0;
}