Function to check if a number is a product of exactly two distinct primes
bool isProduct ( int num ) { int cnt = 0 ; for ( int i = 2 ; cnt < 2 && i * i <= num ; ++ i ) { while ( num % i == 0 ) { num /= i ; ++ cnt ; } } if ( num > 1 ) ++ cnt ; return cnt == 2 ; }