---

#include <stdio.h>

long long fib(int n, long long a, long long b) {
    long long result = a;

    if (n == 1) {
        result = b;
    } else if (n > 1) {
        result = fib(n - 1, b, a + b);
    }

    return result;
}

int main(void) {
    int n = 0;
    int valid = scanf("%d", &n) == 1;

    if (valid) {
        int ch = getchar();

        while (ch == ' ' || ch == '\t' || ch == '\r') {
            ch = getchar();
        }

        valid = ch == '\n' || ch == EOF;
    }

    if (valid && n >= 0 && n <= 92) {
        printf("%lld\n", fib(n, 0, 1));
    } else {
        printf("n/a\n");
    }

    return 0;
}