Ex11.c

#include <stdio.h>

int sum(int n);

int main(int argc, char const *argv[])
{
    int number, result;
    printf("Enter a positive integer: ");
    scanf("%d", &number);

    result = sum(number);

    printf("sum = %d", result);

    return 0;
}

int sum(int n)
{
    if (n != 0)
    {
        // sum() function calls itself
        return n + sum(n - 1);
    }
    else
    {
        return n;
    }
}