#include <iostream>
#include <fstream>
#include <queue>
using namespace std;
#define MAXN 1010
ifstream f("barbar.in");
ofstream g("barbar.out");
queue <int> l,c;
char car;
int a[MAXN][MAXN],b[MAXN][MAXN],n,m,xi,xf,yi,yf,li,lf,ci,cf,dl[]={-1,0,1,0},dc[]={0,-1,0,1};
int main()
{
    f>>n>>m;
    for(int i=1;i<=n;i++)
    for(int j=1;j<=m;j++)
    {
        f>>car;
        if(car=='I')
        {
            xi=i;
            yi=j;
        }
        if(car=='*')
        {
            a[i][j]=-1;
            b[i][j]=-1;
        }
        if(car=='D')
        {
            l.push(i);
            c.push(j);
        }
        if(car=='O')
        {
            xf=i;
            yf=j;
        }
    }
    while(l.size())
    {
        li=l.front();
        ci=c.front();
        l.pop();
        c.pop();
        if(li>0&&li<=n&&ci<=m&&ci>0)
        for(int i=0;i<=3;i++)
        {
            lf=li+dl[i];
            cf=ci+dc[i];
            if(a[lf][cf]==0)
            {
                a[lf][cf]=a[li][ci]+1;
                l.push(lf);
                c.push(cf);
            }
        }
    }
    l.push(xi);
    c.push(yi);
    b[xi][yi]=a[xi][yi];
    while(l.size())
    {
        li=l.front();
        ci=c.front();
        l.pop();
        c.pop();
        if(li>0&&li<=n&&ci>0&&ci<=m)
        for(int i=0;i<=3;i++)
        {
            lf=li+dl[i];
            cf=ci+dc[i];
            if(min(b[li][ci],a[lf][cf])>b[lf][cf])
            {
                b[lf][cf]=min(b[li][ci],a[lf][cf]);
                l.push(lf);
                c.push(cf);
            }
        }
    }
    if(b[xf][yf]!=0&&b[xf][yf]!=-1)
    g<<b[xf][yf];
    else
    g<<-1;


    return 0;
}