#include <fstream>
#define POM -1
using namespace std;
ifstream cin("barbar.in");
ofstream cout("barbar.out");
const int MAX = 1005;
queue < pair<int, int> > q;
int n, m, mat[MAX][MAX], xs, ys, xf, yf;
char ch[MAX][MAX];
int dx[]={0,  0, 1, -1};
int dy[]={1, -1, 0,  0};
void lee()
{
    while(!q.empty())
    {
        int x = q.front().fisrt;
        int y = q.front().second;
        q.pop();
        for(int d=0; d<4; ++d)
            if(mat[ x+dx[d] ][ y+dy[d] ] == )
            {
                mat[ x+dx[d] ][ y+dy[d] ] = mat[x][y] + 1;
                q.push({x+dx[d], y+dy[d]});
            }
    }
}
int main()
{
    cin>>n>>m;
    for(int i=1; i<=n; ++i)
        cin>>ch[i] + 1;
    for(int i=1; i<=n; ++i)
        for(int j=1; j<=m; ++j)
        {
            if(ch[i][j] == 'I')
            {
                xs = i;
                ys = i;
            }
            if(ch[i][j] == 'O')
            {
                xf = i;
                yf = i;
            }
            if(ch[i][j] == 'D')
            {
                mat[i][j] = 1;
                q.push({i, j});
            }
            if(ch[i][j] == '#')
                mat[i][j] = POM;
        }
    init();
    lee();
    i = 0;
    pas = 1<<10;
    while(pas != 0)
    {
        if(se_poate(i+1))
            i+=pas;
        pas /= 2;
    }
    return 0;
}