#include<bits/stdc++.h>
#define NAME ""
#define ll long long
#define F(i,a,b) for(int i=(a);i<(b);++i)
#define fod(i,a,b) for(int i=(a);i<=(b);++i)
#define rep(i,a,b) for(int i=(a);i>=(b);--i)
#define f0(i,n) for(int i=0;i<n;i++)
#define f1(i,n) for(int i=1;i<=n;i++)
#define mii map<int, int>
#define mll map<long long, long long>
#define vi vector<int>
#define vll vector<long long>
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define el "\n"
#define lcm(a, b) (a * b) / __gcd(a, b);
#define ms(f, s) memset(f, s, sizeof(f));
using namespace std;
typedef long double db;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const long long INF=1e18+9;
const int MOD=1e9+7;
const int MAXN=1e6+5;
void file(){
    freopen(NAME".INP","r",stdin);
    freopen(NAME".OUT","w",stdout);
}

int main(){
    ios_base::sync_with_stdio(0);
     cin.tie(0);cout.tie(0);
      //file();
       int N;
    cin >> N;
    vll dp(N+1, 0);
    dp[0] = dp[1] = 1;
    fod(i,2,N) {
        dp[i] = dp[i-1] + dp[i-2];
    }
    cout << dp[N] << endl;
    return 0;
}