#include <stdio.h>
long H(int n,int 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));
}
main()
{
int n,x;
printf("when x=-1,program exits.");
while(1)
{
printf("n=");
scanf("%d",&n);
getchar();
if(n==-1)break;
printf("x=");
scanf("%d",&x);
getchar();
printf("result= %ld\n",H(n,x));
}
}