One-Dimensional Battle Ships CodeForces

本文介绍了一种在一维战舰游戏中检测玩家作弊的方法。通过记录玩家的每次操作并利用集合数据结构来分析游戏状态，可以判断出玩家是否违反了游戏规则。详细介绍了输入输出格式及核心算法。

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lice and Bob love playing one-dimensional battle ships. They play on the field in the form of a line consisting of n square cells (that is, on a 1 × n table).

At the beginning of the game Alice puts k ships on the field without telling their positions to Bob. Each ship looks as a 1 × a rectangle (that is, it occupies a sequence of a consecutive squares of the field). The ships cannot intersect and even touch each other.

After that Bob makes a sequence of "shots". He names cells of the field and Alice either says that the cell is empty ("miss"), or that the cell belongs to some ship ("hit").

But here's the problem! Alice like to cheat. May be that is why she responds to each Bob's move with a "miss".

Help Bob catch Alice cheating — find Bob's first move, such that after it you can be sure that Alice cheated.

Input

The first line of the input contains three integers: n, k and a (1 ≤ n, k, a ≤ 2·10⁵) — the size of the field, the number of the ships and the size of each ship. It is guaranteed that the n, k and a are such that you can put k ships of size a on the field, so that no two ships intersect or touch each other.

The second line contains integer m (1 ≤ m ≤ n) — the number of Bob's moves.

The third line contains m distinct integers x₁, x₂, ..., x_m, where x_i is the number of the cell where Bob made the i-th shot. The cells are numbered from left to right from1 to n.

Output

Print a single integer — the number of such Bob's first move, after which you can be sure that Alice lied. Bob's moves are numbered from 1 to m in the order the were made. If the sought move doesn't exist, then print "-1".

Example

Input

11 3 3
5
4 8 6 1 11

Output

3
找大的和小的 然后巴拉巴拉一处理

 1 #include <iostream>
 2 using namespace std;
 3 #include<string.h>
 4 #include<stdio.h>
 5 #include<set>
 6 #include<map>
 7 #include<algorithm>
 8 #include<math.h>
 9 set<int>TM;
10 int main()
11 {
12      #ifndef ONLINE_JUDGE
13      #endif // ONLINE_JUDGE
14     int haichang,chuanshu,chuanchang;
15     int t,CNM,i;
16     int temp;
17     while(cin>>haichang>>chuanshu>>chuanchang>>t)
18     {
19         TM.clear();
20         int flag=1;
21         TM.insert(0);
22         TM.insert(haichang+1);
23         temp=-1;
24         int sum=(haichang+1)/(chuanchang+1);
25         for(i=1;i<=t;i++)
26         {
27             cin>>CNM;
28             int wei,tou;
29              set<int>::iterator it = TM.upper_bound(CNM);
30              wei=*it;
31 
32              tou=*(--it);
33             sum = sum - (wei-tou)/(chuanchang+1) +(CNM-tou)/(chuanchang+1) + (wei-CNM)/(chuanchang+1);
34             if(sum<chuanshu&&flag)
35             {
36                 flag=0;
37                 temp=i;
38             }
39             TM.insert(CNM);
40         }
41         cout<<temp<<endl;
42     }
43     return 0;
44 }