#include <stdio.h>
#include <stdbool.h>
// 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))  
        printf("yes");  
    else
        printf("no");  
}
/*
run:
yes
*/