wu

#include<bits/stdc++.h>
using namespace std;
int a[31];
int main(){
int n;
cin >> n;
a[1] = 1;
a[2] = 1;
for(int i = 3;i <= n;i++) a[i] = a[i-1]+a[i-2];
cout << a[n];
return 0;
}