#include <iostream>
using namespace std;
int fabi(int n){
    if(n==0 || n==1) return n;
    return fabi(n-2)+fabi(n-1);
}
int main() {
    int a;
    while (cin >> a) { // 注意 while 处理多个 case
        printf("%d",fabi(a));
    }
}