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#include <iostream>
#include <algorithm>
#include <unordered_set>

constexpr int MAXN = 200'004;
constexpr int MAXQ = (1 << 18);

int N, M;
std::unordered_set<int> E[MAXN];
int Q[MAXQ], qf, qr;

void clear() {
    for (int i = 0; i <= N; ++i) E[i].clear();
}

int main() {
    using namespace std;
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int tc;
    cin >> tc;
    for (int t = 1; t <= tc; ++t) {
        cin >> N >> M;
        clear();
        for (int i = 0; i < M; ++i) {
            int x, y;
            cin >> x >> y;
            E[x].insert(y);
            E[y].insert(x);
        }

        qf = qr = 0;
        for (int i = 1; i <= N; ++i) {
            if (E[i].size() == 2) Q[qr++] = i;
        }

        int rm = 0;
        while (qf < qr) {
            const int np = Q[qf++];
            if (E[np].size() != 2) continue;

            auto it = E[np].begin();
            const int e1 = *it;
            const int e2 = *(++it);
            if (E[e1].find(e2) != E[e1].end()) {
                ++rm;
                E[e1].erase(np);
                E[e2].erase(np);
                if (E[e1].size() == 2) Q[qr++] = e1;
                if (E[e2].size() == 2) Q[qr++] = e2;
            }
        }

        cout << "Case #" << t << '\n' << (N - rm) << '\n';
    }
}