#include <iostream>

using namespace std;

int fib(int x) {
    if(x == 1) {
        return 1;
    }
    if(x == 2) {
        return 1;
    }
    return fib(x - 1) + fib(x - 2);
}
int main()
{
    int n;
    cin >> n;
    cout << fib(n) << endl;
    return 0;
}
// fib(7) --> fib(6) + fib(5) = 8 + 5 = 13
// fib(6) --> fib(5) + fib(4) = 5 + 3 = 8
// fib(5) --> fib(4) + fib(3) = 3 + 2 = 5
// fib(4) --> fib(3) + fib(2) = 2 + 1 = 3
// fib(3) --> fib(2) + fib(1) = 1 + 1 = 2
// fib(2) --> 1
// fib(1) --> 1