#include <iostream>
#include <fstream>
#include <vector>
#include <queue>

using namespace std;
queue <pair<int, int> > q;
int vis[1005][1005], vis1[1005][1005];
char a[1005][1005];
int v[1005][1005];
int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0};
pair<int, int> poz;
void bfs(pair<int, int> poz, int n, int m)
{
    int x = poz.first;
    int y = poz.second;
    vis[x][y] = true;
    while (!q.empty())
    {
        poz = q.front();
        x = poz.first;
        y = poz.second;
        q.pop();
        for (int k = 0; k < 4; k++)
        {
            int x1 = x + dx[k];
            int y1 = y + dy[k];
            if (x1 >= 1 and x1 <= n and y1 >= 1 and y1 <= m and a[x1][y1] != 'D' and a[x1][y1] != '*' and !vis[x1][y1])
            {
                v[x1][y1] = v[x][y] + 1;
                vis[x1][y1] = true;
                poz = make_pair(x1, y1);
                q.push(poz);
            }
            if (x1 >= 1 and x1 <= n and y1 >= 1 and y1 <= m and a[x1][y1] == '*' and !vis[x1][y1])
            {
                v[x1][y1] = -1;
                vis[x1][y1] = true;
            }
        }

    }

}
void drum(pair<int, int> paf, int n, int m)
{
    pair<int, int> plecare = paf;
    int ip = paf.first;
    int jp = paf.second;
    int minn = v[ip][jp];
    vis1[ip][jp] = true;
    while (!q.empty())
    {
        bool ok = 0;
        paf = q.front();
        int ip = paf.first;
        int jp = paf.second;
        q.pop();
        for (int k = 0; k < 4; k++)
        {
            int x1 = ip + dx[k];
            int y1 = jp + dy[k];
            if (x1 >= 1 and x1 <= n and y1 >= 1 and y1 <= m and v[x1][y1] >= minn and !vis1[x1][y1])
            {
                ok = 1;
                vis1[x1][y1] = true;
                paf = make_pair(x1, y1);
                q.push(paf);
                if (a[x1][y1] == 'O')
                    while (!q.empty())
                        q.pop();
            }
        }
        if (ok == 0)
        {
            minn--;
            while (!q.empty())
                q.pop();
            q.push(plecare);
            for (int i = 1; i <= n; i++)
            {
                for (int j = 1; j <= m; j++)
                    vis1[i][j] = false;
            }
        }
    }

}

int main()
{
    ifstream fin("barbar.in");
    ofstream fout("barbar.out");
    int n, m, ip, jp, minn;
    pair<int, int> paf;
    fin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            fin >> a[i][j];
            if (a[i][j] == 'I')
                ip = i, jp = j;
            if (a[i][j] == 'D')
            {
                v[i][j] = 0;
                poz = make_pair(i, j);
                q.push(poz);
            }
        }
    }
    bfs(q.front(), n, m);
    minn = v[ip][jp];
    paf = make_pair(ip, jp);
    q.push(paf);
    drum(paf, n, m);
    fout << minn;
    return 0;
}