#include <fstream>
#include <stdio.h>

using namespace std;

#define MAX 1000

void step(char m[MAX][MAX], char check[MAX][MAX], int R, int C, int x, int y, int newx, int newy);

void ver(char m[MAX][MAX], char check[MAX][MAX], int R, int C, int x, int y);

void directie(int x, int y, int &newx, int &newy, int dir);

void peretificare(char marcat[MAX][MAX], int R, int C, int numar);

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

    int R, C, dist, i_start, j_start, i_iesire, j_iesire;
    char m[MAX][MAX], check[MAX][MAX] = {0}, marcat[MAX][MAX] = {0};

    fin >> R >> C;

    for (int i = 0; i < R; i++) {
        for (int j = 0; j < C; j++) {
            fin >> m[i][j];

            if (m[i][j] == 'I') {
                i_start = i;
                j_start = j;

                m[i][j] = '.';
            } else if (m[i][j] == 'O') {
                i_iesire = i;
                j_iesire = j;

                m[i][j] = '.';
            } else if (m[i][j] == '*') {
                marcat[i][j] = 3;
            }
        }
    }

    check[i_start][j_start] = 1;

    ver(marcat, check, R, C, i_start, j_start);

    if (check[i_iesire][j_iesire] == 0) {
        fout << -1;

        return 0;
    }

    for (int i = 0; i < R; i++) {
        for(int j = 0; j < C; j++) {
            if (m[i][j] == 'D') {
                marcat[i][j] = 1;
            }
        }
    }

    if (check[i_iesire][j_iesire] == 0) {
        fout << 0;

        return 0;
    }

    for (dist = 1; dist < max(R, C); dist++) {
        peretificare(marcat, R, C, 2 - dist % 2);

        for (int i = 0; i < R; i++) {
            for (int j = 0; j < C; j++) {
                check[i][j] = 0;
            }
        }

        if (marcat[i_start][j_start] == 0) {
            check[i_start][j_start] = 1;
        } else {
            break;
        }

        ver(marcat, check, R, C, i_start, j_start);

        if (check[i_iesire][j_iesire] != 1) {
            break;
        }
    }

    fout << dist;

    fin.close();
    fout.close();
    return 0;
}

void step(char marcat[MAX][MAX], char check[MAX][MAX], int R, int C, int x, int y, int newx, int newy) {
    if (check[newx][newy] == 0) {
        if (marcat[newx][newy] != 0) {
            check[newx][newy] = 2;
        } else {
            check[newx][newy] = 1;
            ver(marcat, check, R, C, newx, newy);
        }
    }
}

void ver(char marcat[MAX][MAX], char check[MAX][MAX], int R, int C, int x, int y) {
    if (x <= C - 2) {
        step(marcat, check, R, C, x, y, x + 1, y);
    }

    if (y <= R - 2) {
        step(marcat, check, R, C, x, y, x, y + 1);
    }

    if (x >= 1) {
        step(marcat, check, R, C, x, y, x - 1, y);
    }

    if (y >= 1) {
        step(marcat, check, R, C, x, y, x, y - 1);
    }
}

void peretificare(char marcat[MAX][MAX], int R, int C, int numar) {
    int newx, newy;

    for (int i = 0; i < R; i++) {
        for(int j = 0; j < C; j++) {
            if (marcat[i][j] == numar) {
                for(int dir = 0; dir <= 3; dir++) {
                    directie(i, j, newx, newy, dir);

                    if (marcat[newx][newy] == 0) {
                        marcat[newx][newy] = 3 - numar;
                    }
                }
            }
        }
    }
}

void directie(int x, int y, int &newx, int &newy, int dir) {
    if (dir == 0) {
        newx = x - 1;
        newy = y;
    } else if (dir == 1) {
        newx = x;
        newy = y + 1;
    } else if (dir == 2) {
        newx = x + 1;
        newy = y;
    } else if (dir == 3) {
        newx = x;
        newy = y - 1;
    }
}