check the maximum product in diagonal ( going through down - right )
if ( ( i - 3 ) >= 0 && ( j - 3 ) >= 0 ) { result = arr [ i ] [ j ] * arr [ i - 1 ] [ j - 1 ] * arr [ i - 2 ] [ j - 2 ] * arr [ i - 3 ] [ j - 3 ] ; if ( max < result ) max = result ; }