#include <iostream>

int main()
{
    float x, y;
    std::cin >> x;

    if (x > 2) {
        y = 1 / (x * x + 4 * x + 5);
    }
    else {
        y = x * x + 4 * x + 5;
    }

    std::cout << y;
    return 0;
}