#include<stdio.h>

int sum(int n);

int main() {
    printf("sum is : % d",sum(5));
    return 0;
}

//recursive function
int sum(int n) {
    if (n==1)  {
         return 1;
    }
    int sumNm1=sum(n-1);// sum of 1 to n
    int sumN=sumNm1+n;
    return sumN;
}