#include<bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'

vector<int> fa,sz;

int find(int x) // 找根节点
{
    if(fa[x]==x)    return x;
    return fa[x]=find(fa[x]);
}

void uni(int x, int y) // 合并并查集
{
    x=find(x),y=find(y);
    if(x==y)    return;
    if(sz[x]>sz[y]) swap(x,y);
    fa[x]=y;
    sz[y]+=sz[x];
}

void solve() {
    int n,m;
    cin>>n>>m;
    fa.resize(n+1), sz.resize(n+1,1);
    iota(fa.begin(),fa.end(),0);
    int i,j,k,u,v;
    for(i=0;i<m;i++)
    {
        cin>>u>>v;
        uni(u,v);
    }
    map<int,int> mp;
    vector<int> vis(n+1);
    for(i=1;i<=n;i++)
    {
        int t=find(i);
        if(vis[t])
            continue;
        vis[t]=1;
        t=sz[t];
        if(t>=3)    mp[3]++, k=t;
        if(t==2)    mp[2]++;
    }

    cerr<<"end\n";
    if(mp[3]==0)
        cout<<2*mp[2]<<endl;
    else if(mp[3]==1)
        cout<<2*mp[2]+k-1<<endl;
    else
        cout<<0<<endl;
}

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    solve();
}