#include <iostream>
#include <algorithm>
#include <fstream>
#include <cmath>
#include <cstring>
#include <deque>
using namespace std;

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

const int inf=1000000;
int n,m,x,y,ind1,ind2;
int di[4]={0,0,1,-1};
int dj[4]={1,-1,0,0};
int dragon[1005][1005];
int drum[1005][1005];
char lit[1005][1005];
deque< pair<int,int> >coada;

bool bord(int i,int j)
 {
  if(i<1||j<1||i>n||j>m)
    return false;
  return true;
 }

int drg()
 {
  int i,j,ni,nj;
  while( !coada.empty() )
   {
    i=coada.back().first;
    j=coada.back().second;
    coada.pop_back();
    for(int directie=0;directie<4;directie++)
     {
      ni=i+di[directie];
      nj=j+dj[directie];
      if(bord(ni,nj)&&dragon[ni][nj]>dragon[i][j]+1&&lit[ni][nj]!='*')
       {
        dragon[ni][nj]=dragon[i][j]+1;
        coada.push_front(make_pair(ni,nj));
       }
     }
   }
 }

 int lee()
 {
  int i,j,ni,nj;
  while( !coada.empty() )
   {
    i=coada.back().first;
    j=coada.back().second;
    coada.pop_back();
    for(int directie=0;directie<4;directie++)
     {
      ni=i+di[directie];
      nj=j+dj[directie];
      if(bord(ni,nj)&&lit[ni][nj]!='*')
       {
        if(drum[ni][nj]==inf)
         {
          drum[ni][nj]=min(drum[i][j],dragon[ni][nj]);
          coada.push_front(make_pair(ni,nj));
         }
        else
         {
          if(drum[ni][nj]<drum[i][j]&&drum[i][j]<=dragon[ni][nj])
          {
           drum[ni][nj]=drum[i][j];
           coada.push_back(make_pair(ni,nj));
          }
         }
       }
     }
   }
 }
int main()
{
f>>n>>m;
for(int i=1;i<=n;i++)
 for(int j=1;j<=m;j++)
   {
 f>>lit[i][j];
 dragon[i][j]=inf;
 drum[i][j]=inf;
 if(lit[i][j]=='D')
  {
   dragon[i][j]=0;
   coada.push_back(make_pair(i,j));
  }
 if(lit[i][j]=='I')
  {
   x=i; y=j;
  }
 if(lit[i][j]=='O')
  {
   ind1=i; ind2=j;
  }
   }
drg();
drum[x][y]=dragon[x][y];
coada.push_back(make_pair(x,y));
lee();
if(drum[ind1][ind2]!=inf)
g<<drum[ind1][ind2];
else
g<<"-1";
}