1217=蟠桃记

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