#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 25;
vector <int> adj[MAXN];
int dp[MAXN][2];
bool vis[MAXN];
void dfs (int pos, int par) {
vis[pos] = 1;
int mx1 = 0, mx2 = 0, mx3 = 0;
for (auto j : adj[pos]) {
if (j == par) continue;
dfs(j, pos);
if (1 + dp[j][1] > mx1) {
mx2 = mx1; mx1 = dp[j][1];
} else if (dp[j][1] > mx2) {
mx2 = dp[j][1];
}
mx3 = max(mx3, dp[j][0]);
}
dp[pos][0] = max(1 + mx1 + mx2, mx3);
dp[pos][1] = 1 + mx1;
}
int main () {
int mx = 0;
int n, m;
cin >> n >> m;
for (int i = 1; i <= m; i++) {
int a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
}
for (int i = 1; i <= n; i++) {
if (!vis[i]) {
dfs(i, -1);
mx += dp[i][0];
}
}
cout << mx << '\n';
}
