#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<iostream>
#include<vector>
using namespace std;
using i32 = int_fast32_t;
using i64 = int_fast64_t;
#define rep(i, n) for (i32 i = 0; i < (i32)(n); i++)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
using P = pair<i64,i64>;

int main(){
ios::sync_with_stdio(false);
std::cin.tie(nullptr);
i32 n;
cin >> n;
vector<i32> dp(n + 1);
dp[0] = 1;
for(i32 i = 1; i <= n; i++){
    if(i < 2)dp[i] = dp[0];
    else dp[i] = dp[i - 1] + dp[i - 2]; 
}
cout << dp[n] << endl;
}