http://hihocoder.com/problemset/problem/1227
/************************************************
* Author :Powatr
* Created Time :2015/9/21 14:46:41
* File Name :A.cpp
************************************************/
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <cstring>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <bitset>
#include <cstdlib>
#include <ctime>
using namespace std;
#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
typedef long long ll;
const int MAXN = 1e5 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const double EPS = 1e-8;
double x[110], y[110];
double d[11000];
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("%lf%lf", &x[i], &y[i]);
int ans = INF;
for(int i = 1; i <= n; i++){
int pos = 0;
for(int j = 1; j <= n; j++){
d[++pos] = sqrt((x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]));
}
sort(d + 1, d + pos + 1);
int temp = ceil(d[m] + EPS);
if(n == m){
ans = min(ans, temp);
}
else {
if(d[m+1] - temp > 0){
ans = min(ans, temp);
}
}
}
if(ans == INF) puts("-1");
else printf("%d\n", ans);
}
return 0;
}