#include <bits/stdc++.h>
#define PII pair<int,int>
#define TIII tuple <int,int,int>
#define Lin first
#define Col second

using namespace std;

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

int n,m;
int dist[1002][1002];
bool viz[1002][1002];
queue <PII> c;
priority_queue <TIII> Max;
const short int dLin[]={-1,0,1,0},dCol[]={0,1,0,-1};
int iSt,jSt,iFin,jFin;

void citire()
{
    in>>n>>m;

    for(int i=0;i<=n+1;i++)
        viz[i][0]=viz[i][m+1]=1;

    for(int j=0;j<=m+1;j++)
        viz[0][j]=viz[n+1][j]=1;

    char cr;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
        {
            in>>cr;

            switch(cr)
            {
                case '.':
                    break;
                case '*':
                    viz[i][j]=1;
                    break;
                case 'D':
                    viz[i][j]=1;
                    c.push({i,j});
                    break;
                case 'I':
                    iSt=i;jSt=j;
                    break;
                case 'O':
                    iFin=i;jFin=j;
                    break;
            }
        }
}

int main()
{
    citire();

    while(!c.empty())
    {
        int i=c.front().Lin,j=c.front().Col;
        c.pop();

        for(int ip,jp,k=0;k<=3;k++)
            if(!viz[ i+dLin[k] ][ j+dCol[k] ])
            {
                ip=i+dLin[k];
                jp=j+dCol[k];

                dist[ip][jp]=dist[i][j]+1;
                viz[ip][jp]=1;

                c.push({ip,jp});
            }
    }

    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            if(dist[i][j])
                viz[i][j]=0;

    viz[iSt][jSt]=1;
    Max.push( make_tuple( dist[iSt][jSt], iSt, jSt ) );

    while(!Max.empty() && !viz[iFin][jFin])
    {
        int noth,i,j;
        tie(noth,i,j)=Max.top();
        Max.pop();

        for(int ip,jp,k=0;k<=3;k++)
            if(!viz[ i+dLin[k] ][ j+dCol[k] ])
            {
                ip=i+dLin[k];
                jp=j+dCol[k];

                dist[ip][jp]=min(dist[ip][jp],dist[i][j]);
                viz[ip][jp]=1;
                Max.push( make_tuple( dist[ip][jp] , ip, jp ) );
            }
    }

    if(!viz[iFin][jFin])
        out<<-1;
    else
        out<<dist[iFin][jFin];

    return 0;
}