#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <complex>
#include <stack>
#include <queue>
#include <list>
#include <unordered_map>
#include <utility>
#include <map>
#include <set>
using namespace std;

int main(){
    int n;
    int i;
    cin >> n;
    
    long long dp[100];
    
    dp[0] = 1;
    dp[1] = 1;
    
    for(i = 2; i <= n; i++){
        dp[i] = dp[i-1] + dp[i-2];
    }
    
    cout << dp[n] << endl;
}