#include <fstream>
#include <queue>
using namespace std;
ifstream fin("barbar.in");
ofstream fout("barbar.out");
int linii, coloane;
int VeciniX[4] = {-1, 0, 1, 0}, VeciniY[4] = {0, 1, 0, -1};
int MatDragoni[1001][1001];
int CoordXPaft, CoordYPaft, CoordXIesire, CoordYIesire;
int DistMinima = 1, DistMaxima;
struct Punct{
    int x;
    int y;
};
queue<Punct> Dragoni;
bool InMat(Punct P){
    return P.x > 0 && P.x <= linii && P.y > 0 && P.y <= coloane;
}
void Lee(int mat[][1001], queue<Punct> &q, int Type, int Dist){
    while (!q.empty()) {
        Punct frn = q.front();
        for (int i = 0; i < 4; i++) {
            Punct Vecin;
            Vecin.x = frn.x + VeciniX[i];
            Vecin.y = frn.y + VeciniY[i];
            if (InMat(Vecin) && mat[Vecin.x][Vecin.y] == 0) {
                if (Type == 1) {
                    mat[Vecin.x][Vecin.y] = mat[frn.x][frn.y] + 1;
                    q.push(Vecin);
                } else if (MatDragoni[Vecin.x][Vecin.y] > Dist) {
                    mat[Vecin.x][Vecin.y] = mat[frn.x][frn.y] + 1;
                    q.push(Vecin);
                }
            }
        }
        q.pop();
    }
}
bool Merge(int Dist){
    int MatTest[1001][1001] = {0};
    MatTest[CoordXPaft][CoordYPaft] = 1;
    queue<Punct> Paftenie;
    Paftenie.push({CoordXPaft, CoordYPaft});
    Lee(MatTest, Paftenie, 2, Dist);
    if (MatTest[CoordXIesire][CoordYIesire] > 0)
        return true;
    return false;
}
int CautareBinara(int left, int right){
    int rezultat = -1;
    while (left <= right){
        int mid = (left + right)/ 2;
        if (Merge(mid) == false){
            right = mid - 1;
        } else {
            rezultat = mid;
            left = mid + 1;
        }
    }
    return rezultat;
}
int main(){
    fin >> linii >> coloane;
    DistMaxima = linii * coloane;
    for (int i = 1; i <= linii; i++){
        string linie;
        fin >> linie;
        for (int j = 0; j < linie.size(); j++){
            if (linie[j] == 'I'){
                CoordXPaft = i;
                CoordYPaft = j+1;
            } else if (linie[j] == 'D'){
                Punct P;
                P.x = i;
                P.y = j+1;
                Dragoni.push(P);
                MatDragoni[P.x][P.y] = 1;
            } else if (linie[j] == '*'){
                MatDragoni[i][j+1] = -1;
            } else if (linie[j] == 'O'){
                CoordXIesire = i;
                CoordYIesire = j+1;
            }
        }
    }
    Lee(MatDragoni, Dragoni, 1, 0);
    fout << CautareBinara(DistMinima, DistMaxima);
    return 0;
}