#include <iostream>
using namespace std;

int main() {
    int n;
    int fibo[40];
    fibo[0] = 0;
    fibo[1] = 1;
    while (scanf("%d", &n) != EOF) { // 注意 while 处理多个 case
        for(int i = 2; i <= n; i++){
            fibo[i] = fibo[i - 1] + fibo[i - 2];
        }
        printf("%d\n", fibo[n]);
    }
}
// 64 位输出请用 printf("%lld")