#include <fstream>
#include <queue>
using namespace std;

ifstream cin("barbar.in");
ofstream cout("barbar.out");

struct cow
{
    int ox, oy, c;
};

queue <cow> q;
priority_queue <pair<int, pair<int, int>>> pq;

int viz[1005][1005];
int v[1005][1005];
int dx[5]={1, 0, 0, -1};
int dy[5]={0, 1, -1, 0};

int main()
{
    char ch;
    int n, m, x, y, cnt=0, sx, sy, fx, fy, nx, ny, mn=1000005;
    cin>>n>>m;
    for(int i=1; i<=n; i++)
    {
        viz[i][0]=viz[i][n+1]=-1;
        for(int j=1; j<=m; j++)
        {
            viz[0][j]=viz[m+1][j]=-1;
            cin>>ch;
            if(ch=='D')
            {
                q.push({i, j, 0});
                viz[i][j]=1;
            }
            else if(ch=='*')
            {
                viz[i][j]=-1;
            }
            else if(ch=='I')
            {
                sx=i;
                sy=j;
            }
            else if(ch=='O')
            {
                fx=i;
                fy=j;
            }
        }
    }
    while(!q.empty())
    {
        x=q.front().ox;
        y=q.front().oy;
        cnt=q.front().c;
        v[x][y]=cnt;
        q.pop();
        for(int i=0; i<4; i++)
        {
            nx=dx[i]+x;
            ny=dy[i]+y;
            if(viz[nx][ny]==0)
            {
                viz[nx][ny]=1;
                q.push({nx, ny, cnt+1});
            }
        }
    }
    pq.push({v[sx][sy],{sx, sy}});
    while(!pq.empty())
    {
        x=pq.top().second.first;
        y=pq.top().second.second;
        cnt=pq.top().first;
        pq.pop();
        mn=min(mn, cnt);
        if(x==fx && y==fy)
            break;
        for(int i=0; i<4; i++)
        {
            nx=x+dx[i];
            ny=dy[i]+y;
            if(viz[nx][ny]==1)
            {
                viz[nx][ny]=2;
                pq.push({v[nx][ny], {nx, ny}});
            }
        }
    }
    cout<<mn;

    return 0;
}