#include 

using namespace std;


int main()
{
    int n;
    cin >> n;
    int fib[n + 1];
    fib[1] = 1;
    fib[2] = 1;
    for(int i = 3; i <= n; i++) {
        fib[i] = fib[i - 1] + fib[i - 2];
    }
    cout << fib[n] << endl;
    return 0;
}