#include <stdio.h>

int main() {
    int n;
    scanf("%d", &n);
    int fib[41] = {0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55};
    for (int i = 11; i <= n; ++i) {
        fib[i] = fib[i - 1] + fib[i - 2];
    }
    printf("%d\n", fib[n]);
    return 0;
}