#include<cstdio>

struct PUNCT { int x , y ; } ; 

int dx [] = { 1 , 0 , -1 , 0 } ;
int dy [] = { 0 , 1 , 0 , -1 } ; 
const int NMAX = 1<<10;
int n , m , p , u ;
int mat [ NMAX ] [ NMAX ] ;
bool matq [NMAX] [NMAX] ;
PUNCT inceput , sfarsit ;
PUNCT q [ NMAX*NMAX  ] ;
void lee_dragon ( )
{
	int c , xn , yn ;
//	printf ( "LEE DRAGON : p - %d ; u - %d \n" , p , u ) ;
	while ( p <= u )
	{
		for ( c = 0 ; c < 4 ; ++ c )
		{
			xn = q[p].x + dx[c] ;
			yn = q[p].y + dy[c] ;
			if ( mat[xn][yn] != -1 && ( mat[xn][yn] == 0 ) )
			{
				mat[xn][yn]=mat[q[p].x][q[p].y]+1;
				q[++u].x = xn ;
				q[u].y = yn ;
			}
		}
		++p;
	}
}

void init ( ) 
{
	int i , j ;
	for ( i = 1 ; i <= n ; ++ i )
		for ( j = 1 ; j <= m ; ++ j )
			matq[i][j]=false;
}

bool drum ( int damage ) //lee
{
	int xn,yn,c;
	p=u=1;
	q[1] = inceput ;
	bool ajuns = false; 
	init ( ) ;
	if ( mat[q[1].x][q[1].y] <= damage )
		return false;
	while ( p <= u )
	{
		for ( c = 0 ; c < 4 ; ++ c )
		{
			xn = q[p].x + dx[c] ;
			yn = q[p].y + dy[c] ;
			if ( mat[xn][yn] >= damage )
				if ( mat[xn][yn] != -1 && !matq[xn][yn] )
				{
					q[++u].x = xn ;
					q[u].y = yn ;
					if ( q[u].x == sfarsit.x && q[u].y == sfarsit.y )
						return true ;
					matq[xn][yn]=true;
				}
		}
		++p;
		//printf ( "DRUM ( damage - %d ) : p - %d , u - %d\n", damage , p , u ) ;
	}
	return false;
	
}

void afisare ( )
{
	int i , j ;
	for ( i = 1 ; i <= n ; ++ i )
	{
		for ( j = 1 ; j <= m ; ++ j ) 
			printf ( "%2d ", mat[i][j] ) ;
		printf ( "\n" ) ;
	}
}

void caut ( ) 
{
	int pas = 1 << 12 , i ;
	for ( i = 0 ; pas != 0 ; pas >>= 1 )
		if ( drum (i+pas) )
			i+=pas;
	if ( i == 0 )
		printf ( "-1" ) ;
	else
		printf ( "%d ", i - 1) ;
}

void bordare ( )
{
	int i , j ;
	for ( i = 0 ; i <= n + 1 ; ++ i )
		mat[i][0] = mat[i][m+1] = -1 ;
	for ( j = 0 ; j <= m + 1 ; ++ j )
		mat[0][j] = mat[n+1][j] = -1 ;
}



int main ( )
{
	freopen ( "barbar.in", "r", stdin ) ;
	freopen ( "barbar.out", "w", stdout ) ;
	
	int i , j  ;
	char s[NMAX];
	
	scanf ( "%d%d\n", &n,&m ) ;
	
	p=1;
	u=0;
	
	for ( i = 1; i <= n ; ++ i )
	{
		gets ( s ) ;
		for ( j = 0 ; s[j] ; ++ j )
			if ( s[j]=='D' )
			{
				q[++u].x = i ;
				q[u].y = j+1;
				mat[i][j+1]=1;
			}
			else
				if ( s[j] == '*' )
				{
					mat[i][j+1]=-1; 
				}
			else
				if ( s[j] == 'I' )
				{
					inceput.x = i;
					inceput.y = j+1;
				}
				else
					if ( s[j] == 'O' )
					{
						sfarsit.x = i ;
						sfarsit.y = j+1 ;
					}
	}
	/*printf ( "%d\n", u ) ;
	printf ( "%d %d\n" , sfarsit.x , sfarsit.y ) ;*/
	bordare ( ) ;
	lee_dragon ( ) ;
	//afisare ( ) ;
	caut ( ) ;
	
	return 0; 
}