杭电acm 2013题

#include<stdio.h>
int peace(int n,int day);
int main(void)
{
    int n,day;
    while(scanf("%d",&n)!=EOF)
    {
        day=n;
        printf("%d\n",peace(1,day));
    }
    return 0;
}
int peace(int n,int day)
{
    int N;
    if(n==day)
    {
        N=1;
    }
    else
    {
        N=peace(n+1,day)*2+2;
    }
    return N;
}