#include <bits/stdc++.h>
using namespace std;
const int N = 2e5+5;
int x,k;
vector<int>v[N];
int dist[N][2];
bool vis[N][2];
pair<int,int>dfs(int i,bool f){
queue<int>q;
q.push(i);
vis[i][f]=1;
dist[i][f]=1;
int mx=0,pos=i;
while(q.size()){
int j=q.front();q.pop();
if(mx<dist[j][f]){
mx=dist[j][f];
pos=j;
}
for(auto c:v[j]){
if(vis[c][f])continue;
vis[c][f]=1;
dist[c][f]=dist[j][f]+1;
q.push(c);
}
}
return {pos,mx};
}
int main(){
ios::sync_with_stdio(0);cin.tie(0);
cin>>x>>k;
for(int i=0;i<k;i++){
int l,r;cin>>l>>r;
v[l].push_back(r);
v[r].push_back(l);
}
int ans=0;
for(int i=1;i<=x;i++){
if(vis[i][0])continue;
int c=dfs(i,0).first;
ans+=dfs(c,1).second;
}
cout<<ans;
return 0;
}
