#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (int)n; i++)
using ll = long long;

class Union_Find{
  vector<int> par; vector<int> rank; vector<int> num;
public:
  Union_Find(int n) {
    par = vector<int>(n); rank = vector<int>(n,0); num = vector<int>(n,1);
    rep(i,n) par[i] = i;
  }
  int find(int x) {
    if(par[x] == x) return x;
    else  return par[x] = find(par[x]);
  }
  int number(int x) {
    return num[find(x)];
  }
  void unite(int x, int y) {
    x = find(x); y = find(y);
    if (x == y) return;
    if (rank[x] < rank[y]) swap(x, y);
    if (rank[x] == rank[y]) rank[x]++;
    par[y] = x;
    num[x] += num[y];
  } 
  bool same(int x, int y) {
    return find(x) == find(y);
  }
};

int main(){
  int n, m;
  cin >> n >> m;
  vector<int> u(m), v(m);
  rep(i,m) {
    cin >> u[i] >> v[i];
    u[i]--; v[i]--;
  }
  vector<int> dp(n);
  Union_Find uf(n);
  for(int i = m-1; i >= 0; i--) {
    if(uf.same(u[i],v[i])) {
      dp[uf.find(u[i])] = dp[uf.find(u[i])] + 1;
    } else {
      int cur = max(dp[uf.find(u[i])],dp[uf.find(v[i])]);
      uf.unite(u[i],v[i]);
      dp[uf.find(u[i])] = cur+1;
    }
  }
  int ans = 0;
  rep(i,n) ans = max(ans,dp[i]);
  cout << ans << endl;
  return 0;
}