Gym - 101350E Competitive Seagulls (博弈)

There are two seagulls playing a very peculiar game. First they line up N unit squares in a line, all originally colored white.

Let L be the length of the longest continuous sub-segment of white unit squares. Let P be any prime that satisfies the condition that . The player can choose any P if it satisfies the conditions but if there is no value of P that does, then P is set to 1.

The current player then proceeds to choose any continuous sub-segment of white unit squares of length P and paint them black. The player who can’t make a move loses.

If both players play optimally and the first player starts, which player is going to win the game?

Input

The first line of input is T – the number of test cases.

Each test case contains a line with a single integer N (1 ≤ N ≤ 107).

Output

For each test case, output on a single line "first" (without quotes) if the first player would win the game, or "second" if the second would win.

Example

Input
2
2
5
Output
second
first

题意:
每次可以取一段白色连续区间内p个,把白的染成黑色。不能染色的玩家失败。
整段区间内,最长的白色连续区间的长度为L,p是小于等于L/2的任意质数,如果没有质数,p可以取1;
思路:
手推,2,3是先手必败,1是先手必胜。
大于3的偶数,在中间取2,使留下来的两段长度相等。
大于3的奇数,在中间取3,使留下来的两段长度相等。
然后就像nim博弈只有两堆石子那样,跟着第二个人取,就可以坐等胜利了。
#include<cstdio>
int main()
{
    int T;
    scanf("%d",&T);
    while(T--){
        int n;
        scanf("%d",&n);
        if(n==2||n==3){printf("second\n");}
        else printf("first\n");
    }
    return 0;
}
View Code

 


posted @ 2019-04-06 13:10  断腿三郎  阅读(261)  评论(0编辑  收藏  举报