1 #include<cstdio>
2 #include<cstring>
3 #include<cmath>
4 #define MAXM 20
5 #define MAXN 10000
6 #define EPS 1e-8
7 #define INF 0x7FFFFFFF
8 int L[MAXN], R[MAXN], U[MAXN], D[MAXN];
9 int S[MAXN], H[MAXN], C[MAXN], B[MAXN];
10 double dis[MAXM][MAXM];
11 bool vis[MAXM];
12 struct Point {
13 double x, y;
14 };
15 Point p[MAXM], center[MAXN];
16 int n, m, size;
17 inline int dbcmp(double x, double y) {
18 if (fabs(x - y) < EPS)
19 return 0;
20 return x > y ? 1 : -1;
21 }
22 inline double DIS(Point a, Point b) {
23 double x, y;
24 x = b.x - a.x;
25 y = b.y - a.y;
26 return x * x + y * y;
27 }
28 void Init() {
29 int i;
30 for (i = 0; i <= n; i++) {
31 R[i] = i + 1;
32 L[i + 1] = i;
33 U[i] = D[i] = i;
34 S[i] = 0;
35 }
36 R[n] = 0;
37 size = n + 1;
38 }
39 void Link(int r, int c) {
40 D[size] = D[c];
41 U[size] = c;
42 U[D[c]] = size;
43 D[c] = size;
44 if (H[r] < 0)
45 H[r] = L[size] = R[size] = size;
46 else {
47 L[size] = H[r];
48 R[size] = R[H[r]];
49 L[R[H[r]]] = size;
50 R[H[r]] = size;
51 }
52 S[c]++;
53 C[size++] = c;
54 }
55 int A() {
56 int i, j, k, res;
57 memset(vis, false, sizeof(vis));
58 for (res = 0, i = R[0]; i; i = R[i]) {
59 if (vis[i])
60 continue;
61 res++;
62 for (j = D[i]; j != i; j = D[j]) {
63 for (k = R[j]; k != j; k = R[k])
64 vis[C[k]] = true;
65 }
66 }
67 return res;
68 }
69 void Remove(int c) {
70 int i;
71 for (i = D[c]; i != c; i = D[i]) {
72 L[R[i]] = L[i];
73 R[L[i]] = R[i];
74 }
75 }
76 void Resume(int c) {
77 int i;
78 for (i = D[c]; i != c; i = D[i])
79 L[R[i]] = R[L[i]] = i;
80 }
81 bool Dance(int now) {
82 if (now + A() > m)
83 return false;
84 if (R[0] == 0)
85 return true;
86 int i, j, temp, c;
87 for (temp = INF,i = R[0]; i; i = R[i]) {
88 if (temp > S[i]) {
89 temp = S[i];
90 c = i;
91 }
92 }
93 for (i = D[c]; i != c; i = D[i]) {
94 Remove(i);
95 for (j = R[i]; j != i; j = R[j])
96 Remove(j);
97 if (Dance(now + 1))
98 return true;
99 for (j = L[i]; j != i; j = L[j])
100 Resume(j);
101 Resume(i);
102 }
103 return false;
104 }
105 void Center(int i, int j, double r, int &cnt) {
106 double x0, y0, x1, y1, d;
107 if (dbcmp(dis[i][j], 0) == 0)
108 center[cnt++] = p[i];
109 else if (dbcmp(dis[i][j], 2 * r) == 0) {
110 center[cnt].x = (p[i].x + p[j].x) / 2;
111 center[cnt++].y = (p[i].y + p[j].y) / 2;
112 } else if (dbcmp(dis[i][j], 2 * r) < 0) {
113 x0 = (p[i].x + p[j].x) / 2;
114 y0 = (p[i].y + p[j].y) / 2;
115 x1 = (p[i].x - p[j].x) / 2;
116 y1 = (p[i].y - p[j].y) / 2;
117 d = sqrt(r * r - x1 * x1 - y1 * y1) / dis[i][j];
118 center[cnt].x = (p[j].y - p[i].y) * d + x0;
119 center[cnt++].y = (p[i].x - p[j].x) * d + y0;
120 center[cnt].x = (p[i].y - p[j].y) * d + x0;
121 center[cnt++].y = (p[j].x - p[i].x) * d + y0;
122 }
123 }
124 bool OK(double r) {
125 int i, j, k, cnt;
126 Init();
127 for (cnt = 0, i = 1; i <= n; i++) {
128 for (j = i; j <= n; j++)
129 Center(i, j, r, cnt);
130 }
131 for (r *= r, i = 0; i < cnt; i++) {
132 H[i] = -1;
133 B[i] = 0;
134 for (j = 1; j <= n; j++) {
135 B[i] <<= 1;
136 if (dbcmp(DIS(center[i], p[j]), r) <= 0)
137 B[i] |= 1;
138 }
139 }
140 for (i = 0; i < cnt; i++) {
141 for (j = i + 1; j < cnt; j++) {
142 if ((B[i] | B[j]) == B[j])
143 break;
144 }
145 if (j == cnt) {
146 for (k = 0; k < n; k++) {
147 if (B[i] & (1 << k))
148 Link(i, k + 1);
149 }
150 }
151 }
152 return Dance(0);
153 }
154 int main() {
155 int T, i, j;
156 double low, high, mid;
157 scanf("%d", &T);
158 while (T--) {
159 scanf("%d%d", &n, &m);
160 for (i = 1; i <= n; i++)
161 scanf("%lf%lf", &p[i].x, &p[i].y);
162 for (i = 1; i <= n; i++) {
163 dis[i][i] = 0;
164 for (j = i + 1; j <= n; j++)
165 dis[i][j] = dis[j][i] = sqrt(DIS(p[i], p[j]));
166 }
167 for (low = 0, high = 15; dbcmp(low, high) < 0;) {
168 mid = (low + high) / 2;
169 if (OK(mid))
170 high = mid;
171 else
172 low = mid;
173 }
174 printf("%lf\n", low);
175 }
176 return 0;
177 }
