#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 100100;
int dp[2][N];
vector<int> adj[N];
bool vis[N];
int mx;
void dfs(int v, int p = -1) {
vis[v] = 1;
for (auto& x : adj[v]) {
if (x == p) continue;
dfs(x, v);
dp[1][v] = max(dp[1][v], dp[0][x] + 1);
if (dp[0][v] < dp[1][v]) swap(dp[0][v], dp[1][v]);
}
mx = max(mx, dp[0][v] + dp[1][v] + 1);
}
int main() {
cin.tie(nullptr)->sync_with_stdio(false);
int n, m;
cin >> n >> m;
while (m--) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
int ans = 0;
for (int i = 1;i <= n;i++) {
if (vis[i]) continue;
mx = 0;
dfs(i);
ans += mx;
}
cout << ans << '\n';
return 0;
}
