/*************************************************************************

> File Name: 1051.cpp

> Author: dulun

> Mail: dulun@xiyoulinux.org

> Created Time: 2016年04月09日 星期六 21时33分19秒

************************************************************************/

#include<iostream>

#include<stdio.h>

#include<cstring>

#include<cstdlib>

#include<algorithm>

#define LL long long

using namespace std;

const int N = 50086;

int total = 100;

int ans = 0;

int a[200];

bool v[N];

int main()

{

int T;

scanf("%d", &T);

while(T--)

{

int n, m;

scanf("%d %d", &n, &m);

for(int i=1; i<=n; i++) scanf("%d", &a[i]);

if(m>=n) { printf("100\n"); continue; }

a[0] = 0, a[n+1] = 101;

int ans = 0;

for(int i=0; i<=n; i++)

{

if(i+m+1 > n+1) break;

int p = a[i+m+1] - a[i] - 1;

if(ans<p) ans = p;

}

printf("%d\n", ans);

}

return 0;

}