#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1000;
int n, k;
int x[MAXN + 5], y[MAXN + 5];
struct Edge
{
    int u, v, w; // w存距离的平方、减少开方运算的次数
};
vector<Edge> e;
bool cmp(Edge x, Edge y)
{
    return x.w < y.w;
}
int fa[MAXN + 5];
int findFa(int x)
{
    if (x == fa[x])
        return x;
    return fa[x] = findFa(fa[x]);
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> k;
    for (int i = 1; i <= n; i++)
        cin >> x[i] >> y[i];

    for (int i = 1; i <= n; i++)
        for (int j = i + 1; j <= n; j++)
        {
            int len = (x[i] - x[j]) * (x[i] - x[j]) +
                      (y[i] - y[j]) * (y[i] - y[j]);
            e.push_back({i, j, len});
        }
    sort(e.begin(), e.end(), cmp);
    for (int i = 1; i <= n; i++)
        fa[i] = i;

    int num = n; // 连通块数量
    int ans = 0;
    for (int i = 0; i <= (int)e.size() - 1; i++)
    {
        int u = e[i].u, v = e[i].v, w = e[i].w;
        int faU = findFa(u);
        int faV = findFa(v);
        if (faU == faV)
            continue;
        fa[faU] = faV;
        num--;
        if (num == k - 1)
        {
            ans = w;
            break;
        }
    }

    cout << fixed << setprecision(2) << sqrt(ans);
    return 0;
}