#include<bits/stdc++.h>
using namespace std;

const int N=50;

int f[N];

int main(){
	
	int n;
	cin>>n;
	
	if(n<=2){
		cout<<1<<endl;
		return 0;
	}
	
	f[1]=1;f[2]=1;
	
	for(int i=3;i<=n;i++){
		f[i]=f[i-1]+f[i-2];
	}
	
	cout<<f[n]<<endl;
    return 0;
}