#include <bits/stdc++.h>
using namespace std;

int n;

long long memo[100][2] = {};

long long dp(int i, int ok){
        if(i >= n){
                return 1;
        }
        if(memo[i][ok] != -1) return memo[i][ok];
        if(i == n-1) return memo[i][ok] = dp(i+1, 0);

        return memo[i][ok] = dp(i+1, 0) + dp(i+2, 0);
}



int main(){
        cin >> n;
        memset(memo, -1, sizeof(memo));
        cout << dp(0, 0) << endl;

        return 0;
}