1 #include<iostream>
2 #include<stack>
3 #include<cstdio>
4 using namespace std;
5 const int N = 12000;
6
7 struct edge{
8 int to;
9 int next;
10 }e[N];
11
12 int n,m;
13 int tot;
14 int head[N];
15 int dfn[N];
16 int low[N];
17 int id[N];
18 int t;
19 int cnt;
20 int ru[N];
21 int ans;
22
23 stack <int> st;
24
25 void add(int x,int y){
26 tot++;
27 e[tot].to = y;
28 e[tot].next = head[x];
29 head[x] = tot;
30 }
31
32 void tarjan(int x,int ok){
33 low[x] = dfn[x] = ++t;
34 st.push(x);
35 for(int i=head[x];i;i=e[i].next){
36 int y = e[i].to;
37 if(!dfn[y]){
38 tarjan(y,i);
39 low[x] = min(low[x],low[y]);
40 }
41 else if(i != (ok^1))
42 low[x] = min(low[x],dfn[y]);
43 }
44 if(low[x] == dfn[x]){
45 int k;
46 cnt++;
47 while(k != x){
48 k = st.top();
49 st.pop();
50 id[k] = cnt;
51 }
52 }
53 }
54
55 int main(){
56 scanf("%d%d",&n,&m);
57 tot=1;
58 for(int i=1;i<=m;i++){
59 int x,y;
60 scanf("%d%d",&x,&y);
61 add(x,y);
62 add(y,x);
63 }
64 for(int i=1;i<=n;i++)
65 if(!dfn[i])tarjan(i,-1);
66 for(int x=1;x<=n;x++){
67 for(int i=head[x];i;i=e[i].next){
68 int y = e[i].to;
69 if(id[x] == id[y]) continue;
70 ru[id[y]]++;
71 }
72 }
73 for(int i=1;i<=cnt;i++)
74 if(ru[i] == 1)ans++;
75 ans = (ans + 1)/2;
76 printf("%d\n",ans);
77 return 0;
78 }
