When previous rows had { white , black }
if ( row1 && ! row2 ) { ans = ( ( ( ans + Ways ( col + 1 , comp , 0 , 0 ) ) + Ways ( col + 1 , comp , 1 , 1 ) ) + Ways ( col + 1 , comp , 1 , 0 ) ) ; ans = ( ans + Ways ( col + 1 , comp + 2 , 0 , 1 ) ) ; }