代码：
// Created by CAD on 2019/9/18.
#include <bits/stdc++.h>
using namespace std;
const int maxn=1e5+5;
int fa[maxn];
inline int find(int x)
{
return x==fa[x]?fa[x]:fa[x]=find(fa[x]);
}
void merge(int x,int y)
{
int fx=find(x),fy=find(y);
if(fx!=fy) fa[fx]=fy;
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int n,m; cin>>n>>m;
for(int i=1;i<=n;++i) fa[i]=i;
int u,v,ans=0;
for(int i=1;i<=m;++i)
{
cin>>u>>v;
if(find(u)==find(v)) ans++;
merge(u,v);
}
cout<<ans<<endl;
return 0;
}