HDU 2064 汉诺塔III(递归)

#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <cstring>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#include <map>
#define PI 3.1415926
#define ms(a) memset(a,0,sizeof(a))
#define msp memset(mp,0,sizeof(mp))
#define msv memset(vis,0,sizeof(vis))
using namespace std;
//#define LOCAL
int a[100005],b[100005];
long long fun(int n)
{
    if(n==1)return 2;
    return 3*fun(n-1)+2;
}
int main()
{
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
#endif // LOCAL
    //Start
    int n;
    while(cin>>n)
    {
        long long ans=fun(n);
        printf("%I64d\n",ans);
    }
    return 0;
}