#include <iostream>
using namespace std;

int main() {
	int n;
	cin>>n;
	int a=1,b=1,c;
	for(int i=2;i<=n;i++){
		c=a+b;
		a=b;
		b=c;
	}
	if(n==0 || n==1)
	   cout<<1;
	else
	    cout<<b;
	    
	return 0;
}