#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <limits.h>
#include <map>
#include <queue>
#include <string.h>
#include <vector>

using namespace std;
typedef long long ll;

const int MAX_N = 200000;
vector<int> _parent;
vector<int> _rank;
vector<int> _size;

class UnionFind {
public:
  UnionFind(int n) {
    for (int i = 0; i < n; ++i) {
      _parent.push_back(i);
      _rank.push_back(0);
      _size.push_back(1);
    }
  }

  int find(int x) {
    if (_parent[x] == x) {
      return x;
    } else {
      return _parent[x] = find(_parent[x]);
    }
  }

  void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return;

    if (_rank[x] < _rank[y]) {
      _parent[x] = y;
      _size[y] += _size[x];
    } else {
      _parent[y] = x;
      _size[x] += _size[y];
      if (_rank[x] == _rank[y]) ++_rank[x];
    }
  }

  bool same(int x, int y) {
    return find(x) == find(y);
  }

  int size(int x) {
    return _size[find(x)];
  }
};

int main() {
  int N, M;
  cin >> N >> M;

  UnionFind uf(N + 1);
  vector<int> counter(N + 1, 0);
  int U[M];
  int V[M];
  for (int i = 0; i < M; ++i) {
    cin >> U[i] >> V[i];
  }

  for (int i = M - 1; i >= 0; --i) {
    int u = U[i];
    int v = V[i];
    int p1 = uf.find(u);
    int p2 = uf.find(v);

    if (uf.same(u, v)) {
      counter[p1]++;
    } else {
      uf.unite(u, v);
      int p = uf.find(u);
      counter[p] = max(counter[p1], counter[p2]) + 1;
    }
  }

  cout << counter[uf.find(1)] << endl;

  return 0;
}