/**
 * @author : cyb1010
 * @date   : 2024-04-11 08:17:09
 * @file   : triangle.cpp
 */
#include <bits/stdc++.h>
using namespace std;
namespace FastIO {
const std::size_t buf_size = 1 << 18;
char I[buf_size], *p1, *p2, O[buf_size], s[128];
int p, q, f;
inline char gc() {
    return p1 == p2 && (p2 = (p1 = I) + fread(I, 1, sizeof(I), stdin), p1 == p2)
               ? EOF
               : *p1++;
}
inline void pc(char c) { O[p++] = c; }
inline void flush() { fwrite(O, 1, p, stdout), p = 0; }
void chkf() {
    if (p >= buf_size >> 1) flush();
}
struct AutoFlush {
    ~AutoFlush() { flush(); }
} auto_flush;

template <typename T>
void rd(T &x) {
    char c = gc();
    x = 0, f = c == '-';
    while (!isdigit(c)) c = gc(), c == '-' ? f = 1 : 0;
    while (isdigit(c)) x = x * 10 + c - '0', c = gc();
    f ? x = -x : 1;
}
template <typename T>
void wr(T x) {
    if (x < 0) x = -x, pc('-');
    do s[++q] = (x % 10) | 48;
    while (x /= 10);
    do pc(s[q]);
    while (--q);
    chkf();
}
template <typename T>
void wr(T x, char c) {
    wr(x), pc(c);
}
} // namespace FastIO
using FastIO::rd;
using FastIO::wr;
#define fo(s) freopen(s ".in", "r", stdin), freopen(s ".out", "w", stdout)
#define fi first
#define se second
typedef double db;
typedef long double ldb;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<db, db> pii;
const int N = 1000010;
int __, n, _;
pii a[N];
db ans = 1e12;
multiset<pii> S;
db sq(db x) { return x * x; }
db dis(pii x, pii y) { return sqrt(sq(x.fi - y.fi) + sq(x.se - y.se)); }
int main() {
    rd(_);
    for (int I = 1; I <= _; I++) {
        rd(n), S.clear();
        for (int i = 1; i <= n; i++) rd(a[i].fi), rd(a[i].se);
        sort(a + 1, a + 1 + n);
        for (int i = 1; i <= n; i++) swap(a[i].fi, a[i].se);
        for (int i = 1, L = 1; i <= n; i++) {
            while (a[L].se + ans / 2 <= a[i].se) S.erase(S.find(a[L++]));
            auto x = S.upper_bound({a[i].fi - ans / 2, 0}),
                 y = S.upper_bound({a[i].fi + ans / 2, 0});
            for (auto p = x; p != y; p = next(p))
                for (auto q = x; q != p; q = next(q))
                    ans = min(ans, dis(*p, a[i]) + dis(*q, a[i]) + dis(*p, *q));
            S.insert(a[i]);
        }
        printf("Case #%d: %.14lf\n", I, ans);
    }
    return 0 ^ __ ^ 0;
}