#include <iostream>
using namespace std;

int main()
{
	int N;
	while(cin>>N)
	{
		int number[25]={0};
		number[1]=1;
		number[2]=2;
		int x=2;
		if(N>2)
			while(x++!=N)
				number[x]=number[x-1]+number[x-2];
		cout<<number[N]<<endl;
	}
	return 0;
}