#include <iostream>
using namespace std;

int f [99];

int fib (int n) {
    if (f[n] == 0) {
        if (n < 2) f[n] = n;
        else f[n] = fib (n - 1) + fib (n - 2);
    }
    return f[n];
}

int main () {
    int n;
    while (cin >> n)
        cout << fib (n) << endl;
    return 0;
}