#include<stdio.h>   

int main(){ 
	int i,n,sum=0;
	scanf("%d",&n);
	if(n % 2 == 0){  //判断n是偶数还是奇数 

		for(i = 1;i <= n;i++){
			if(n % i == 0){  //判断i是不是n的约数 
				sum += i; 
			}
		}
	}else{
		for(i = 1;i <= n;i++){  
			if(i % 2 == 0){
				sum += i;
			}
		}
	}
		
	printf("%d",sum);
	return 0;
} 
/**************************************************************
	Problem: 1060
	User: admin
	Language: C
	Result: Accepted
	Time:9 ms
	Memory:1144 kb
****************************************************************/