#include <iostream>
#include <fstream>
#define MAX 1001

using namespace std;

char a[MAX][MAX];
bool seen[MAX][MAX];
short int lindir[] = {-1, 0, 1, 0}, coldir[] = {0, 1, 0, -1};

struct
{
    int x;
    int y;
}coada[MAX * MAX], dragoni[MAX * MAX];

bool verificare(int x, int y, int n, int m, int contor, int limita)
{
    if(x >= 1 && x <= n && y >= 1 && y <= m && !seen[x][y] && a[x][y] != '*')
    {
        int i;

        for(i = 1; i <= contor; i++)
            if(abs(dragoni[i].x - x) + abs(dragoni[i].y - y) < limita)return false;

        return true;
    }

    return false;
}

void clean(int n, int m)
{
    int i, j;

    for(i = 1; i <= n; i++)
        for(j = 1; j <= m; j++)
            seen[i][j] = 0;
}

bool lee(int n, int m, int limita, int pornireX, int pornireY, int exitX, int exitY, int contor)
{
    int lin, col, i, st, dr;

    st = dr = 1;

    coada[st].x = pornireX;
    coada[st].y = pornireY;

    seen[pornireX][pornireY] = 1;

    while(st <= dr)
    {
        for(i = 0; i <= 3; i++)
        {
            lin = coada[st].x + lindir[i];
            col = coada[st].y + coldir[i];

            if(verificare(lin, col, n, m, contor, limita))
            {
                dr++;

                coada[dr].x = lin;
                coada[dr].y = col;

                seen[lin][col] = 1;
            }
        }

        st++;
    }

    return seen[exitX][exitY];
}

int main()
{
    int n, m, contor, i, j, pornireX, pornireY, exitX, exitY, st, dr, mij, sol;

    ifstream fin("barbar.in");
    ofstream fout("barbar.out");

    fin >> n >> m;

    contor = 0;

    for(i = 1; i <= n; i++)
    {
        fin >> a[i];
        for(j = m; j > 0; j--)
        {
            a[i][j] = a[i][j - 1];

            if(a[i][j] == 'D')
            {
                contor++;
                dragoni[contor].x = i;
                dragoni[contor].y = j;
            }
            else if(a[i][j] == 'I')
            {
                pornireX = i;
                pornireY = j;
            }
            else if(a[i][j] == 'O')
            {
                exitX = i;
                exitY = j;
            }
        }
    }

    st = 1;
    dr = n + m - 2;

    sol = -1;

    while(st <= dr)
    {
        mij = (st + dr) / 2;

        clean(n, m);
        if(lee(n, m, mij, pornireX, pornireY, exitX, exitY, contor))
        {
            sol = mij;

            st = mij + 1;
        }
        else dr = mij - 1;
    }

    fout << sol;

    return 0;
}