Stores the product of every pair of prime number
vector < long long > prod ; SieveOfEratosthenes ( ) ; int l = primes . size ( ) ; for ( int i = 0 ; i < l ; i ++ ) { for ( int j = i + 1 ; j < l ; j ++ ) { if ( primes [ i ] * primes [ j ] > 0 ) prod . push_back ( primes [ i ] * primes [ j ] ) ; } }