#include<stdio.h>
#include<stdlib.h>

int sum(int a)
{
    if(a==1)
   	 	return 1;
    else
    	return a+sum(a-1);
}


int main()
{
    int n;
    printf("Enter number: ");
    scanf("%d",&n);
    
    printf("%d \n",sum(n));
    
    system("pause");
}