#include<bits/stdc++.h>
using namespace std;
int main(){
    int n; cin >> n;
    int f[50];
    f[0] = 1;
    f[1] = 1;
    for(int i = 2; i < 50; i++) f[i] = f[i-1] + f[i-2];
    cout << f[n] << endl;
    return 0;
}
