#pragma GCC optimize("Ofast")
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdio>
#include <ctime>
#include <assert.h>
#include <chrono>
#include <random>
#include <numeric>
#include <set>
#include <deque>
#include <stack>
#include <sstream>
#include <utility>
#include <cstring>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}

struct UnionFind{
    vector<int> par,num;
    UnionFind(int n):par(n),num(n,1){
        iota(par.begin(),par.end(),0);  //include<numeric>
    }
    int find(int v){
        return (par[v]==v)?v:(par[v]=find(par[v]));
    }
    void unite(int u,int v){
        u=find(u),v=find(v);
        if(u==v)return;
        if(num[u]<num[v])swap(u,v);
        num[u]+=num[v];
        par[v]=u;
    }
    bool same(int u,int v){
        return find(u) == find(v);
    }
    int size(int v){
        return num[find(v)];
    }
};

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n,m; cin >> n >> m;
    vector<vector<int>> g(n);
    for(int i=0;i<m;i++){
        int x,y; cin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }
    vector<int> used(n);
    vector<int> imos_v(n);
    vector<int> deg(n);
    int sz = 0;
    UnionFind uf(n);
    vector<int> pa(n,-1);
    vector<vector<int>> G(n); // 縮約後のグラフ
    int res = 0;
    for(int i=0;i<n;i++){
        if(!used[i]){
            sz++;
            used[i]=1;
            vector<int> v;
            auto dfs=[&](auto dfs,int s,int p)->void{
                bool par = false;
                v.push_back(s);
                for(int t:g[s]){
                    if(t==p and !par){
                        par = true;
                    }
                    else if(!used[t]){
                        pa[t] = s;
                        deg[s]++;
                        used[t]=used[s]+1;
                        dfs(dfs,t,s);
                    }
                    else if(used[s]<used[t])continue;
                    else{
                        imos_v[t]--;
                        imos_v[s]++;
                    }
                }
            };
            dfs(dfs,i,-1);
            queue<int> q;
            for(int i:v){
                if(deg[i] == 0){
                    q.push(i);
                }
            }
            while(q.size()){
                int s = q.front(); q.pop();
                if(pa[s] != -1){
                    if(imos_v[s] != 0){
                        uf.unite(s, pa[s]);
                    }
                    imos_v[pa[s]] += imos_v[s];
                    deg[pa[s]]--;
                    if(deg[pa[s]] == 0){
                        q.push(pa[s]);
                    }
                }
            }
            for(int i:v){
                if(pa[i] != -1){
                    if(!uf.same(pa[i],i)){
                        int s = uf.find(i);
                        int t = uf.find(pa[i]);
                        G[s].push_back(t);
                        G[t].push_back(s);
                    }
                }
            }
        }
    }
    vector<int> d(n,-1);
    for(int i=0;i<n;i++){
        if(d[i] == -1){
            vector<int> v;
            queue<int> q;
            q.push(i);
            d[i] = 0;
            while(q.size()){
                int s = q.front(); q.pop();
                v.push_back(s);
                for(int t:G[s]){
                    if(d[t] == -1){
                        d[t] = d[s]+1;
                        q.push(t);
                    }
                }
            }
            int mx = i;
            for(int &j:v){
                if(d[mx] < d[j])mx = j;
            }
            for(int &j:v){
                d[j] = -1;
            }
            d[mx] = 0;
            q.push(mx);
            while(q.size()){
                int s = q.front(); q.pop();
                v.push_back(s);
                for(int t:G[s]){
                    if(d[t] == -1){
                        d[t] = d[s]+1;
                        q.push(t);
                    }
                }
                mx = d[s];
            }
            res += mx;
        }
    }
    cout << res + sz - 1 << endl;
}