C语言：蟠桃

#include <stdio.h>
main()
{
    int days,sum=1;
    scanf("%d",&days);
    while(--days)
    {
        sum=(sum+1)*2;
    }
    printf("%d",sum);

    getchar();
 }

#include <stdio.h>
int f(int n){
    if(n==1) return 1;
    else return 2*(f(n-1)+1);
}
main()
{
    int n,a,b,c;
    scanf("%d",&n);
    b=f(n);
    printf("%d",b);
     



    getchar();
 }