#include <iostream>
// A pronic number is a number which is the product of two consecutive integers
// 42 = 6 * 7 -> yes 6 and 7 is consecutive integers
// 45 = 5 * 9 -> no 5 and 9 is not consecutive integers
 
bool isPronicNumber(int num) {  
    for (int i = 1; i <= num; i++) {  
        if ((i * (i + 1)) == num) {  
            return true;
        }  
    }  
    return false;  
}  
 
int main(void) {
    int num = 42;
     
    if (isPronicNumber(num))  
        std::cout << "yes";  
    else
        std::cout << "no";  
}
 
 
 
 
 
/*
run:
 
yes
 
*/