#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e6 + , INF = 0x7fffffff;

int n, m, s, t, flag;

vector<int> G[maxn];

int vis[maxn], res;

void dfs(int u, int fa)

{

    vis[u] = ;

    for(int i=; i<G[u].size(); i++)

    {

        int v = G[u][i];

        if(v == fa) continue;

        if(vis[v])

        {

            s = v;

            if(G[u].size() != ) flag = ;　　//判断是否在一个简单环中

            return;

        }

        else

        {

            dfs(v, u);

            if(G[u].size() != ) flag = ;

            break;

        }

    }

    if(flag ==  && s == u)

        res++;

}

int main()

{

    int u, v;

    res = ;

    cin >> n >> m;

    for(int i=; i<m; i++)

    {

        cin >> u >> v;

        G[u].push_back(v);

        G[v].push_back(u);

    }

    for(int i=; i<=n; i++)

    {

        if(!vis[i])

        {

            s = INF, flag = ;

            dfs(i, -);

        }

    }

    cout << res << endl;

    return ;

}