Subsequence of length 4 of type 1 1 2 2
for ( i = 0 ; i < n ; i ++ ) { for ( j = i + 1 ; j < n ; j ++ ) { if ( a [ i ] == 1 && a [ j ] == 1 && suff [ j ] >= 2 ) { ss += ( suff [ j ] ) * ( suff [ j ] - 1 ) / 2 ; } } }