// 斐波那契数列记忆化递归
#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1e5 + 3;
int dep[N]; 

int fib(int a){
    if(a <= 2) return 1;
    if(dep[a] != -1) return dep[a];
    return dep[a] = fib(a-1) + fib(a-2);
}
signed main(){
    fill(dep, dep + N, -1);
    int n; cin >> n;
    cout << fib(n) << endl;
    return 0;
}
/*
1 1 2 3 5 8 13 21 34
*/