蟠桃记

#include<stdio.h>
int fun(int x)
{
 int sum=1,i;
 for(i=x;i>1;i--)
   sum=2*sum+2;
 return sum;
}
int main( )
{
 int N;
 while(scanf("%d",&N)!=EOF)
 printf("%d\n",fun(N));
 return 0;
}