#include <iostream>
using namespace std;

const int limit = 51;
_int64 fib[limit];

int main()
{
    int num;
    fib[0] = 0;
    fib[1] = 1;
    for (int i = 2; i <= limit; i++)
    {
        fib[i] = fib[i - 1] + fib[i - 2];
    }
    
    while (cin >> num && num!=-1)
    {
        cout << fib[num] << endl;
    }
    return 0;
}