problem 42

#include <stdio.h>

int sum(int n);

int main() {
    int n, add;
    printf("Enter a value of n: ");
    scanf("%d", &n);

    add = sum(n);
    printf("%d", add);

    return 0;
}

int sum(int n) {
    if (n == 1 || n == 0) return 1;
    int addans = n + sum(n - 1);
    return addans;
}

Enter a value of n: