#include <iostream>

#include <fstream>

#include <queue>



#define l first

#define c second



using namespace std;



const int NMAX = 1002;



ifstream fin("barbar.in");

ofstream fout("barbar.out");



int N, M;

int sl, sc, fl, fc;



int dl[] = { 1, -1, 0, 0 };

int dc[] = { 0, 0, 1, -1 };



queue < pair <int,int> > Q;

int Mat[NMAX][NMAX];

bool V[NMAX][NMAX];



void Read()

{

    char c;

    fin >> N >> M;



    for( int i = 1; i <= N; ++i )Mat[i][0] = Mat[i][M+1] = -1;

    for( int i = 1; i <= M; ++i )Mat[0][i] = Mat[N+1][i] = -1;



    for( int i = 1; i <= N; i -=- 1 )

        for( int j = 1; j <= M; j -=- 1)

    {

        fin >> c;

        if( c == 'I' )

        {

            sl = i;

            sc = j;

        }

        if( c == 'O')

        {

            fl = i;

            fc = j;

        }

        if( c == 'D' )

        {

            Q.push( make_pair(i,j) );
            V[i][j] = 1;
            //Mat[i][j] = -1;

        }

        if( c == '*' )

        {

            Mat[i][j] = -1;

        }

    }



    /*for( int i = 0; i <= N+1; ++i )

    {

        for( int j = 0; j <= M+1; ++j )

        {

            if( Mat[i][j] == -1 )

                fout << '#' << ' ';

            else fout << Mat[i][j] << ' ';

        }

        fout << '\n';

    }*/

}



void Solve()

{

    int x, y, xv, yv;

    while( Q.size() )

    {

        x = Q.front().l;

        y = Q.front().c;

        Q.pop();



        for( int k = 0; k < 4; ++k )

        {

            xv = x + dl[k];

            yv = y + dc[k];



            if( Mat[xv][yv] == 0 && V[xv][yv] == 0 )

            {

                Mat[xv][yv] = Mat[x][y] + 1;

                Q.push( make_pair( xv, yv ) );

            }

        }

    }

    priority_queue < pair<int,pair<int, int> > > PQ;

    PQ.push( make_pair(Mat[fl][fc],make_pair (fl, fc)) );

    V[fl][fc] = 1;



    while( PQ.size() )

    {
        int v = PQ.top().l;
        x = PQ.top().c.l;

        y = PQ.top().c.c;

        PQ.pop();



        for( int k = 0; k < 4; ++k )

        {

            xv = x + dl[k];

            yv = y + dc[k];



            if( Mat[xv][yv] != -1 && V[xv][yv] == 0)

            {

                V[xv][yv] = 1;

                Mat[xv][yv] = min( Mat[xv][yv], v );
                PQ.push(make_pair(Mat[xv][yv],make_pair(xv,yv)));

            }

        }

    }

    int S = V[sl][sc] ? Mat[sl][sc] : -1;
    fout << S;
}

int main()

{

    Read();

    Solve();

    return 0;

}