#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;

#define PI         acos(-1.0)
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)

typedef long long ll;

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