//Microsoft (R) C/C++ Optimizing Compiler Version 19.00.23506 for x64

#include
#include
using namespace std;
int main()
{
    size_t N = 0U;
    double f = 1.f;
    cin >> N;
    if (N >= 2)
        for (size_t i = 2; i <= N; ++i)
            f *= 1 - (1 / pow(i, 2));
    else cout < 2" << endl;
   cout << f;
}