#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<vector<int>> matrix;
#define sx first
#define sy second

string file = "file";
ifstream f(file + ".in");
ofstream g(file + ".out");

ll n, m, xi, yi, xo, yo;
matrix v, dist, costs;
string s;
deque<pair<int, int>> d;
const int dx[] = { 0 , 0 , 1 , -1 }, dy[] = { 1 , -1 , 0 , 0 };


void test2d()
{
    for (ll i = 1; i <= n; i++)
    {
        for (ll j = 1; j <= m; j++)
        {
            g << v[i][j] << " ";
        }
        g << endl;
    }
    g << endl;
    for (ll i = 1; i <= n; i++)
    {
        for (ll j = 1; j <= m; j++)
        {
            g << dist[i][j] << " ";
        }
        g << endl;
    }
    g << endl;
    for (ll i = 1; i <= n; i++)
    {
        for (ll j = 1; j <= m; j++)
        {
            g << costs[i][j] << " ";
        }
        g << endl;
    }
    g << endl;
}

void init()
{
    f >> n >> m;
    v.resize(n + 5);
    dist.resize(n + 5);
    costs.resize(n + 5);

    v[0].resize(m + 5, -1);
    dist[0].resize(m + 5, -1);
    costs[0].resize(m + 5, -1);
    for (ll i = 1; i <= n; i++)
    {
        v[i].resize(m + 5, -1);
        dist[i].resize(m + 5, -1);
        costs[i].resize(m + 5, -1);
        f >> s;
        for (ll j = 1; j <= m; j++)
        {
            char cs = s[j - 1];
            if (cs == '.') v[i][j] = 1;
            else if (cs == '*') v[i][j] = 2;
            else if (cs == 'D') v[i][j] = 3, d.push_back({ i, j });
            else if (cs == 'I') v[i][j] = 1, xi = i, yi = j;
            else if (cs == 'O') v[i][j] = 1, xo = i, yo = j;
        }
    }
    v[n + 1].resize(m + 5, -1);
    dist[n + 1].resize(m + 5, -1);
    costs[n + 1].resize(m + 5, -1);
}

void dragons()
{
    while (d.size())
    {
        int x = d.front().sx, y = d.front().sy;
        if (dist[x][y] == -1 && v[x][y] == 3) dist[x][y] = 0;
        d.pop_front();
        for (int k = 0; k < 4; k++)
        {
            ll nx = x + dx[k], ny = y + dy[k];
            if (dist[nx][ny] == -1 && v[nx][ny] != -1)
            {
                dist[nx][ny] = dist[x][y] + 1;
                d.push_back({ nx, ny });
            }
            else if (dist[nx][ny] > 0)
            {
                dist[nx][ny] = min(dist[nx][ny], dist[x][y] + 1);
            }
        }
    }
}

void path()
{
    costs[xi][yi] = dist[xi][yi];
    d.push_back({ xi, yi });
    while (d.size())
    {
        int x = d.front().sx, y = d.front().sy;
        d.pop_front();
        //g << x << " " << y << " " << dist[x][y] << " " << minn << endl;
        for (int k = 0; k < 4; k++)
        {
            ll nx = x + dx[k], ny = y + dy[k];
            if (v[x][y] == v[nx][ny] && costs[nx][ny] == -1)
            {
                if (costs[x][y] <= dist[nx][ny])
                {
                    costs[nx][ny] = costs[x][y];
                    d.push_front({ nx, ny });
                }
                else if (costs[x][y] > dist[nx][ny])
                {
                    costs[nx][ny] = dist[nx][ny];
                    d.push_back({ nx, ny });
                }
            }
        }
    }
}

int main()
{
    init();
    dragons();
    path();
    //test2d();
    g << costs[xo][yo];
    return 0;
}