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#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<stack>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<string>
#include<cmath>
using namespace std;
#define ll long long
#define rep(i,n) for(int i =0; i < n; ++i)
#define CLR(x) memset(x,0,sizeof x)
#define MEM(a,b) memset(a,b,sizeof a)
#define pr(x) cout << #x << " = " << x << " ";
#define prln(x) cout << #x << " = " << x << endl;
const int maxn = 4e5+100;
const int INF = 0x3f3f3f3f;
int dfn[maxn], low[maxn];
int head[maxn];
int ans;
int dfnnum, edgenum = 0;
struct Edge{
int v, nxt;
}edge[maxn];
void addedge(int u, int v){
edge[edgenum].nxt = head[u];
edge[edgenum].v = v;
head[u] = edgenum++;
}
int vis[maxn];
int in[maxn];
void tarjan(int fa, int u) {
dfn[u] = ++dfnnum;
low[u] = dfn[u];
for(int i = head[u]; ~i; i = edge[i].nxt){
int v = edge[i].v;
if(in[i]) continue;
in[i^1] = in[i] = true;
if(!dfn[v]){
tarjan(i|1,v);
low[u] = min(low[u], low[v]);
if(low[v] > dfn[u]){
ans++;
}
}else low[u] = min(low[u], dfn[v]);
}
}
void clear(){
MEM(head,-1);
MEM(dfn,0);
MEM(in,0);
MEM(vis,0);
edgenum = 0;
dfnnum = 0;
ans = 0;
}
int main(){
#ifdef LOCAL
freopen("/home/zeroxf/桌面/in.txt","r",stdin);
#endif
int t, n, m;
int kase = 0;
scanf("%d", &t);
while(t--){
scanf("%d%d", &n, &m);
int u, v, root;
clear();
for(int i = 0; i < m; ++i){
scanf("%d%d", &u, &v);
addedge(u,v);
addedge(v,u);
}
for(int i = 1; i <= n; ++i){
if(!dfn[i]) tarjan(-1,i);
}
printf("Case %d: ",++kase);
printf("%d\n",ans);
}
return 0;
}
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