取石子游戏——斐波那契博弈

1堆石子有n个,两人轮流取.先取者第1次可以取任意多个，但不能全部取完.以后每次取的石子数不能超过上次取子数的2倍。取完者胜.先取者负输出”Second win”.先取者胜输出”First win”.
Input
输入有多组.每组第1行是2<=n<2^31. n=0退出.
Output
先取者负输出”Second win”. 先取者胜输出”First win”.
参看Sample Output.
Sample Input
2
13
10000
0
Sample Output
Second win
Second win
First win

#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cmath>
#define ll long long int 
#define ull unsigned long long int 
#pragma warning(disable:4996)
#define pf printf
#define sf scanf
using namespace std;

int main(void) {
    int fib[50];

    fib[0] = 2; fib[1] = 3;

    for (int i = 2; i < 50; i++)
        fib[i] = fib[i - 1] + fib[i - 2];//从2开始
    int n;

    while (sf("%d", &n), n) {

        int i;
        bool flag = true;
        for (i = 0; i < 50; i++) {
            if (fib[i] == n) {
                puts("Second win");
                flag = false;

            }
            else if (fib[i] > n)  break;
        }
        if (flag)
            puts("First win");
    }

    return 0;
}