文件目录

#include <iostream>
using namespace std;
double h(int n, double x)
{
    if (n == 0)
        return 1;
    if (n == 1)
        return 2 * x;
    if (n > 1)
        return 2 * x * h(n - 1, x) - 2 * (n - 1) * h(n - 2, x);
}
int main()
{
    int n;
    double x;
    cin >> n >> x;
    printf("%.2lf", h(n, x));
    return 0;
}