/*
 * recursive fibonacci function and main program to call it.
 */
#include <stdio.h>
#include <stdlib.h>

/* returns n-th element of fibonacci sequence */
long fibonacci(int n) {
    if (n <= 1) 
        return 1;
    else 
        return fibonacci(n-1) + fibonacci(n-2);
}

/* main program */
int main(void) {
    printf("which element?\n");
    int n;
    if ((scanf("%d", &n) == 1) && (n >= 0)) {
        printf("%ld\n", fibonacci(n));
        return EXIT_SUCCESS;
    }
    else {
        printf("input must be a non-negative integer\n");
        return EXIT_FAILURE;
    }
}