#include <fstream>
#include <vector>
#include <queue>
#include <set>

using namespace std;

ifstream in("barbar.in");
ofstream out("barbar.out");
int n, m;
int v[1005][1005];
vector<pair<int, int>> dragoni;
int dist[1005][1005];
int viz[1005][1005];
int istart, jstart;
int ifin, jfin;
queue<pair<int, int>> q;
multiset<pair<int, pair<int, int>>> st;
//{dist, {i, j}}
int di[] = {1, -1, 0, 0};
int dj[] = {0, 0, 1, -1};

int main()
{
    in>>n>>m;

    string s;
    for(int i = 1; i<=n; i++)
    {
        in>>s;

        for(int j = 1; j<=m; j++)
        {
            if(s[j - 1] == '.')
            {
                v[i][j] = 0;
            }
            else if(s[j - 1] == '*')
            {
                v[i][j] = -1;
            }
            else if(s[j - 1] == 'D')
            {
                dragoni.push_back({i, j});
                v[i][j] = -1;
            }
            else if(s[j - 1] == 'I')
            {
                v[i][j] = 0;
                istart = i;
                jstart = j;
            }
            else if(s[j - 1] == 'O')
            {
                v[i][j] = 0;
                ifin = i;
                jfin = j;
            }
        }
    }

    //out<<ifin<<" "<<jfin<<'\n';

    for(auto it: dragoni)
    {
        q.push(it);

        dist[it.first][it.second] = 1;

        //out<<it.first<<" "<<it.second<<'\n';
    }

    int i, j, iv, jv, d;
    while(!q.empty())
    {
        i = q.front().first;
        j = q.front().second;

        q.pop();

        for(int k = 0; k<4; k++)
        {
            iv = i + di[k];
            jv = j + dj[k];

            if(iv >= 1 && iv <= n && jv >= 1 && jv <= m && dist[iv][jv] == 0 && v[iv][jv] == 0)
            {
                q.push({iv, jv});

                dist[iv][jv] = dist[i][j] + 1;
            }
        }
    }

    /*for(int i = 1; i<=n; i++)
    {
        for(int j = 1; j<=m; j++)
        {
            out<<dist[i][j]<<" ";
        }
        out<<'\n';
    }*/

    st.insert({dist[istart][jstart] * (-1), {istart, jstart}});
    viz[istart][jstart] = 1;

    while(!st.empty())
    {
        d = (*st.begin()).first * (-1);
        i = (*st.begin()).second.first;
        j = (*st.begin()).second.second;

        //out<<i<<" "<<j<<" -> "<<d<<'\n';

        st.erase(st.begin());

        if(i == ifin && j == jfin)
        {
            //out<<i<<" "<<j<<'\n';
            out<<d - 1;

            return 0;
        }

        for(int k = 0; k<4; k++)
        {
            iv = i + di[k];
            jv = j + dj[k];

            if(iv >= 1 && iv <= n && jv >= 1 && jv <= m && viz[iv][jv] == 0 && v[iv][jv] == 0)
            {
                int dmin = min(d, dist[iv][jv]);
                st.insert({dmin * (-1), {iv, jv}});

                viz[iv][jv] = 1;
            }
        }
    }

    out<<-1;

    return 0;
}