#include <stdio.h>
float func(int n, int x)
{
    float fn;
    if (n == 0) return 1;
    if (n == 1) return x;

    fn = (float)n;
    return ((2 * fn - 1) * x * func(n - 1, x) - (fn - 1) * func(n - 2, x)) / fn;
}
int main()
{
    int n;
    float x;
    printf("input n,x:");
    scanf("%d,%f", &n, &x);
    printf("%.2f\n", func(n, x));
    return 0;
}