#include <fstream.h>
#include <string.h>
#define MAX 1005
ifstream fin ("barbar.in");
ofstream fout ("barbar.out");

const int x[4]={-1,0,0,1};
const int y[4]={0,-1,1,0};

int n,a[MAX][MAX],m,xi,yi,xf,yf,mat[MAX][MAX];

void citire()
{
   fin>>n>>m;
     char s[1010];
   fin.getline(s,1010);
   for (int i=1;i<=n;i++)
   {
      fin.getline (s,1010);
	for (int j=1;j<strlen(s)+1;j++)
	{
	    if (s[j-1]=='.')
	       a[i][j]=-1;
	    else
	      if (s[j-1]=='*')
		 a[i][j]=-2;
		 else
		    if (s[j-1]=='D')
		       a[i][j]=0;
		    else
		      if (s[j-1]=='I')
		      {
			a[i][j]=-3;
			xi=i;
			yi=j;
		      }
		      else
			if (s[j-1]=='O')
			{
			   a[i][j]=-3;
			   xf=i;
			   yf=j;
			}
	}
   }

}

int max(int a,int b)
{
   if (a<b)
     return a;
     return b;
}

void umplu()
{

  int p;
   for (p=0;p<n+1;p++)
   {
      a[p][0]=-2;
      a[p][m+1]=-2;
   }

   for (p=0;p<m+1;p++)
   {
      a[0][p]=-2;
      a[n+1][p]=-2;
   }

   memset(mat,9,sizeof(mat));
   for (int i=1;i<=n;i++)
     for (int j=1;j<=m;j++)
	if (a[i][j]==0)
	{
	  int ii=i,jj=j;
	  for (int k=0;k<4;k++)
	  {
	     int nr=0;
	     ii=i;
	     jj=j;
	     while (a[ii][jj]!=-2)
	     {
		 mat[ii][jj]=max(mat[ii][jj],nr);
		 nr++;
		 ii+=x[k];
		 jj+=y[k];
	      }
	  }
	}
}

int min(int a,int b)
{
  if (a<b)
     return a;
  return b;
}

void fac()
{
   int xx[1000000],yy[1000000];
   int nr=1;
   xx[0]=xi;
   yy[0]=yi;
   int nr1=0;
   while (nr){
      nr1=0;
   for (int i=0;i<nr;i++)
      for (int k=0;k<4;k++)
	 if ( a[xx[i] +x[k]][yy[i] +y[k]] !=-2)
	 {
	   if (nr<999990){
	    mat[xx[i] +x[k]][yy[i] +y[k]]=min(mat[xx[i] +x[k]][yy[i] +y[k]],mat[xx[i]][yy[i]]);
	    xx[nr]=xx[i]+x[k];
	    yy[nr]=yy[i]+y[k];
	    nr++;
	    }
	    else
	    {
	    mat[xx[i] +x[k]][yy[i] +y[k]]=min(mat[xx[i] +x[k]][yy[i] +y[k]],mat[xx[i]][yy[i]]);
	    xx[nr1]=xx[i]+x[k];
	    yy[nr1]=yy[i]+y[k];
	    nr1++;
	    }
	 }
      nr=nr1;
   }
}

int main ()
{
   citire();
   umplu();
   fac();
   if (mat[xf][yf]==9)
      fout<<-1<<"\n";
   else
      fout<<mat[xf][yf]<<"\n";
   fout.close();
   fin.close();
   return 0;
}