#include<stdio.h>
#include<queue>
#include<vector>
#include<cmath>
using namespace std;
#define MAX_NODE 505
//点的数据结构
struct Point{int x;int y;
};
vector<Point> gPoints;//边的数据结构
struct Edge{int from;int to;double dist;Edge(int f, int t, double d) :from(f), to(t), dist(d){};
};
vector<Edge> gEdges;//计算两点之间的距离
double Dist(const Point& p1, const Point& p2){return sqrt(1.0*(p1.x - p2.x)*(p1.x - p2.x) + (p1.y - p2.y)*(p1.y - p2.y));
}//用并查集来判断加入一条边是否会构成环
int gRoot[MAX_NODE];
int GetRoot(int c){if (gRoot[c] != c){gRoot[c] = GetRoot(gRoot[c]);}return gRoot[c];
}
bool SameRoot(int c1, int c2){int p1 = GetRoot(c1);int p2 = GetRoot(c2);return p1 == p2;
}void Union(int c1, int c2){int p1 = GetRoot(c1);int p2 = GetRoot(c2);gRoot[p1] = p2;
}
//用于对边进行排序
bool Compare(const Edge& e1, const Edge& e2){return e1.dist < e2.dist;
}double Kruskal(int s, int n){double result;for (int i = 0; i < n; i++){gRoot[i] = i;}sort(gEdges.begin(), gEdges.end(), Compare); //无向图的边只存储了 从序号较小的节点指向序号较大的节点int count = 0;for (int i = 0; i < gEdges.size(); i++){Edge& e = gEdges[i];if (SameRoot(e.from, e.to))continue;count++;if (count == n - s){ //从最小生成树中的n-1条边，去掉最大的s-1条边（因为有s个卫星站，相当于s个点，则s-1条边）//，剩下的n-1-s条边中，最大的边长即为所求result = e.dist;return result;}Union(e.to, e.from);//gRoot[gRoot[e.to]] = gRoot[e.from]; //注意合并的时候，将 to 的根更新为 from的根。因为所有的边只存储了从小序号指向大序号}return 0;
}int main(){int cas, s, p;Point point;scanf("%d", &cas);while (cas--){scanf("%d %d", &s, &p);gEdges.clear();gPoints.clear();for (int i = 0; i < p; i++){scanf("%d %d", &point.x, &point.y);for (int j = 0; j < i; j++){double dist = Dist(point, gPoints[j]);gEdges.push_back(Edge(j, i, dist));}gPoints.push_back(point);}double result = Kruskal(s, p);printf("%.2lf\n", result);}return 0;
}