/*
Computes the Sum of numbers from 1 to N
-prints the recursion tree

n        sum
1        1
2        3
3        6
4        10
5        15
6        21


*/

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

#define N 3

int sum(int n)
{
     int res;
     printf("At recursive call %d\n", n);
     if(n == 1)     //base case
        return 1;
        
     res = sum(n-1);
     
     printf("in call %d, returned from call %d with value %d\n", n, n-1, res);
     return n + res;  //recursive case
}

int main()
{
    int x;
    x = sum(N);
    printf("\n\nsum of %d down to 1 is %d\n\n", N, x);
    system("pause");
}