#include <iostream>
#include <fstream>
#include <queue>
#include <utility>
#define INF 0x3f3f3f
#define mp make_pair
#define nmax 1005
using namespace std;

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

queue< pair<int,int> > q;

int R, C, d[nmax][nmax], p[nmax][nmax];
int ix, iy, ox, oy;
char c;

void bordeaza()
{
    for ( int i=0; i<=R+1; ++i )
    {
        d[i][0] = d[i][C+1] = -1;
        p[i][0] = p[i][C+1] = INF;
    }

    for ( int i=0; i<=C+1; ++i )
    {
        d[0][i] = d[R+1][i] = -1;
        p[0][i] = p[R+1][i] = INF;
    }
}

void distanteDragoni()
{
    int i, j;

    while ( !q.empty() )
    {
        i = q.front().first;
        j = q.front().second;
        q.pop();

        if ( !d[i-1][j] )
            d[i-1][j] = d[i][j] + 1, q.push( mp(i-1, j) );

        if ( !d[i][j+1] )
            d[i][j+1] = d[i][j] + 1, q.push( mp(i, j+1) );

        if ( !d[i+1][j] )
            d[i+1][j] = d[i][j] + 1, q.push( mp(i+1, j) );

        if ( !d[i][j-1] )
            d[i][j-1] = d[i][j] + 1, q.push( mp(i, j-1) );
    }
}

void parcurgere()
{
    int i, j, dist;
    q.push( mp(ix, iy) );

    p[ix][iy] = d[ix][iy];

    while( !q.empty() )
    {
        i = q.front().first;
        j = q.front().second;
        q.pop();

        dist = min ( p[i][j], d[i-1][j] );
        if ( p[i-1][j] < dist )
            p[i-1][j] = dist, q.push( mp(i-1, j) );

        dist = min ( p[i][j], d[i][j+1] );
        if ( p[i][j+1] < dist )
            p[i][j+1] = dist, q.push( mp(i, j+1) );

        dist = min ( p[i][j], d[i+1][j] );
        if ( p[i+1][j] < dist )
            p[i+1][j] = dist, q.push( mp(i+1, j) );


        dist = min ( p[i][j], d[i][j-1] );
        if ( p[i][j-1] < dist )
            p[i][j-1] = dist, q.push( mp(i, j-1) );

    }
}

int main()
{
    in >> R >> C;
    bordeaza();

    for ( int i=1; i<=R; ++i )
        for ( int j=1; j<=C; ++j )
        {
            in >> c;
            switch(c)
            {
                case 'D':
                    p[i][j] = INF;
                    q.push( mp(i, j) );
                    break;
                case '*':
                    d[i][j] = -1;
                    p[i][j] = INF;
                    break;
                case 'I':
                    ix = i;
                    iy = j;
                    break;
                case 'O':
                    ox = i;
                    oy = j;
                    break;
            }

        }


    distanteDragoni();

    parcurgere();

    if ( !p[ox][oy] ) out << -1;
        else out << p[ox][oy];
}