#include <iostream>
using namespace std;

int main()
{
    long long ladder[100];

    ladder[1] = 1;
    ladder[2] = 2;

    for(int i=3;i<100;i++)
        ladder[i] = ladder[i-1] + ladder[i-2];

	int input;
    while(cin>>input)
	{
        cout<<ladder[input]<<endl;
	}

    return 0;
}