#include<bits/stdc++.h>
using namespace std;
int a[50500],b[50500],c[50500];
int len = 1;
int jia(){
	int j = 0;
	for(int i = 1;i <= len;i ++){
		c[i] = b[i] + a[i] + j;
		j = c[i] / 10;
		c[i] %= 10;
	}
	if(j != 0){
		len ++;
		c[len] = j;
	}
	for(int i = 1;i <= len;i ++){
		a[i] = b[i];
		b[i] = c[i];
	}
}
int main(){
	int n;
	cin>>n;
	a[1] = 1;
	b[1] = 1;
	for(int i = 2;i <= n;i ++) jia();
	for(int i = len;i >= 1;i --) cout<<b[i];
	return 0;
}