#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
int main() {
  int N, M, ans = 0;
  cin >> N >> M;
  dsu uf(N);
  vector<int> u(M), v(M), dp(N);
  for( int i = 0; i < M; i++ ) {
    cin >> u[i] >> v[i];
    u[i]--; v[i]--;
  }
  reverse(u.begin(), u.end());
  reverse(v.begin(), v.end());
  for( int i = 0; i < M; i++ ) {
    int ul = uf.leader(u[i]), vl = uf.leader(v[i]), m = max(dp[ul], dp[vl]);
    dp[ul] = m+1;
    dp[vl] = m+1;
    uf.merge(u[i], v[i]);
  }
  for( int i = 0; i < N; i++ ) {
    ans = max(ans, dp[i]);
  }
  cout << ans << endl;
}