根据递推公式计算，需要打表不然可能会超时。

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<list>
#include<cmath>
#include<string>
#include<sstream>
#include<ctime>
using namespace std;
#define _PI acos(-1.0)
#define INF (1 << 10)
#define esp 1e-6
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int> pill;
/*===========================================
===========================================*/
#define MAXD 50
int m;
LL f[MAXD];
LL g[MAXD];
LL _g(int _n){
    LL ans = (1 << _n) - f[_n];
    return ans;
}
LL solve(int _n){
    if(_n < 3)
        f[_n] = 0;
    else{
        LL ans = (1 << (_n - 3));
        for(int i = 2 ; i <= _n - 2 ; i++){
            ans += g[i - 2] * (1 << (_n - i - 2));
        }
        f[_n] = ans;
    }
    g[_n] = _g(_n);
    return f[_n];
}
int main(){
    memset(f,-1,sizeof(f));
    LL ans ;
    for(int i = 0 ; i <= 30 ; i++)
       ans = solve(i);
    while(scanf("%d",&m) && m){
         printf("%lld\n",f[m]);
    }
    return 0;
}