//
//  main.c
//  barbar
//
//  Created by Alexandru Bâgu on 1/13/14.
//  Copyright (c) 2014 Alexandru Bâgu. All rights reserved.
//

#include <stdio.h>
#define MAX 1000
int M[MAX][MAX], Mn[MAX][MAX], V[MAX][MAX], Md[MAX][MAX];
typedef struct { int x, y; } COORD;
COORD Ds[MAX * MAX];
int ds = 0, end = 0;

int abs(int x) { if(x < 0) return -x; return x; }
int min(int a, int b) { if(a < b) return a; return b; }
int max(int a, int b) { if(a > b) return a; return b; }

int add_d(int x, int y)
{
    Ds[ds].x = x;
    Ds[ds].y = y;
    ds++;
    return 0;
}
int d_dist(int x, int y)
{
    int i, _min = 10000;
    for(i = 0; i < ds; i++)
        _min = min(_min, abs(x - Ds[i].x) + abs(y - Ds[i].y));
    return _min;
}
int avail(int a) { return a != -1 && a != -3; }
int lee(int,int);

int go_lee(int x, int y, int pDist)
{
    if(x == 0 || y == 0) return 0;
    if(!avail(M[x][y])) return 0;
    if(M[x][y] == -2) end = 1;
    if(V[x][y] == 0 || (V[x][y] == 1 && pDist > Md[x][y]))
    {
        V[x][y] = 1;
        Md[x][y] = min(pDist, Mn[x][y]);
        lee(x,y);
    }
    return 0;
}

int lee(int x, int y)
{
    int d = Md[x][y];
    go_lee(x, y - 1, d);
    go_lee(x, y + 1, d);
    go_lee(x - 1, y, d);
    go_lee(x + 1, y, d);
    return 0;
}
int main(int argc, const char * argv[])
{
    freopen("barbar.in", "r", stdin);
    freopen("barbar.out", "w", stdout);
    int n, m, i, j, si, sj, ei, ej;
    char x;
    scanf("%d%d", &n, &m);
    
    for(i = 0; i < MAX; i++)
        for(j = 0; j < MAX; j++)
            M[i][j] = -3, Mn[i][j] = 0, V[i][j] = 0;
    
    for(i = 1; i <= n; i++)
    {
        for(j = 1; j <= m; j++)
        {
            do { scanf("%c", &x); } while (x == '\n');
            if(x == '.') M[i][j] = 1;
            else if(x == '*') M[i][j] = -1;
            else if(x == 'I') { M[i][j] = 0; si =i; sj = j; }
            else if(x == 'D') { add_d(i,j); M[i][j] = 1000; }
            else if(x == 'O') { M[i][j] = -2; ei = i; ej = j; }
        }
    }
    for(i = 1; i <= n; i++)
        for(j = 1; j <= m; j++)
            Mn[i][j] = d_dist(i,j);
    Md[si][sj] = Mn[si][sj];
    lee(si, sj);
    /*for(i = 0; i <= n + 1; i++) {
        for(j = 0; j <= n + 1; j++)
            printf("%d ", Md[i][j]);
        printf("\n");
    }*/
    if(!end) printf("-1");
    else printf("%d", Md[ei][ej]);
    return 0;
}