#include <bits/stdc++.h>
#define pi pair<int, int>
#define pb push_back
#define inf 1e7
using namespace std;

const string file = "barbar";
ifstream fin(file+".in");
ofstream fout(file+".out");

const int di[] = {-1, 0, 0, 1}, dj[] = {0, -1, 1, 0};
int n, m, i, j, drm[1001][1001], drum[1001][1001];
char a[1001][1001];
queue<pi> q;

bool inmat(int i, int j)
{
    return i >= 1 && i <= n && j >= 1 && j <= m;
}

void lee(int d[1001][1001])
{
    while (!q.empty())
    {
        auto top = q.front();
        q.pop();
        int x = top.first, y = top.second;
        for (int k = 0; k < 4; k++)
        {
            int dx = x+di[k], dy = y+dj[k];
            if (inmat(dx, dy) && a[dx][dy] != '*' && d[dx][dy] > d[x][y]+1)
            {
                d[dx][dy] = d[x][y]+1;
                q.push({dx, dy});
            }
        }
    }
}

void lee2(int d[1001][1001])
{
    while (!q.empty())
    {
        auto top = q.front();
        q.pop();
        int x = top.first, y = top.second;
        for (int k = 0; k < 4; k++)
        {
            int dx = x+di[k], dy = y+dj[k];
            if (inmat(dx, dy) && a[dx][dy] != '*' && d[dx][dy] < min(d[x][y], drm[dx][dy]))
            {
                d[dx][dy] = min(d[x][y], drm[dx][dy]);
                q.push({dx, dy});
            }
        }
    }
}

int main()
{
    fin >> n >> m;
    int nrd = 0, stx, sty, fx, fy;
    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++)
        {
            drm[i][j] = inf;
            drum[i][j] = 0;
            fin >> a[i][j];
            if (a[i][j] == 'D')
                q.push({i, j}), drm[i][j] = 0, nrd++;
            else if (a[i][j] == 'I')
                stx = i, sty = j;
            else if (a[i][j] == 'O')
                fx = i, fy = j;
        }
    if (!nrd)
    {
        fout << -1;
        return 0;
    }
    lee(drm);

    q.push({stx, sty});
    drum[stx][sty] = drm[stx][sty];
    lee2(drum);
    fout << drum[fx][fy];
    return 0;
}