#include "bits/stdc++.h"
using namespace std;
#define pb push_back
#define endl "\n"
#define int long long
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
constexpr int N = 1e5 + 5;
vector<int> v[N];
int vis[N];
array<int,2> cur;
void dfs(int c,int p,int d){
cur=max(cur,{d,c});
vis[c]=1;
for(int x:v[c]){
if(x==p) continue;
dfs(x,c,d+1);
}
}
void solve(){
int n,m;
cin >> n >> m;
for(int i=1;i<=m;i++){
int a,b;
cin >> a >> b;
v[a].pb(b);
v[b].pb(a);
}
int ans=0;
for(int i=1;i<=n;i++){
if(vis[i]) continue;
ans++;
cur={0,0};
dfs(i,i,0);
dfs(cur[1],cur[1],0);
ans+=cur[0];
}
cout << ans << endl;
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
int t=1;//cin >> t;
while(t--) solve();
return 0;
}
