/* -*- coding: utf-8 -*-
 *
 * 2072.cc:  No.2072 Anatomy - yukicoder
 */

#include<cstdio>
#include<vector>
#include<algorithm>
#include<utility>
 
using namespace std;

/* constant */

const int MAX_N = 200000;
const int MAX_M = 200000;

/* typedef */

typedef pair<int,int> pii;

struct UFT {
  vector<int> links, ranks, sizes;
  UFT() {}

  void init(int n) {
    links.resize(n);
    for (int i = 0; i < n; i++) links[i] = i;
    ranks.assign(n, 1);
    sizes.assign(n, 1);
  }

  int root(int i) {
    int i0 = i;
    while (links[i0] != i0) i0 = links[i0];
    return (links[i] = i0);
  }

  int rank(int i) { return ranks[root(i)]; }
  int size(int i) { return sizes[root(i)]; }
  bool same(int i, int j) { return root(i) == root(j); }

  int merge(int i0, int i1) {
    int r0 = root(i0), r1 = root(i1), mr;
    if (r0 == r1) return r0;
    if (ranks[r0] == ranks[r1]) {
      links[r1] = r0;
      sizes[r0] += sizes[r1];
      ranks[r0]++;
      mr = r0;
    }
    else if (ranks[r0] > ranks[r1]) {
      links[r1] = r0;
      sizes[r0] += sizes[r1];
      mr = r0;
    }
    else {
      links[r0] = r1;
      sizes[r1] += sizes[r0];
      mr = r1;
    }
    return mr;
  }
};

/* global variables */

pii es[MAX_M];
UFT uft;
int ds[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  for (int i = 0; i < m; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    u--, v--;
    es[i] = pii(u, v);
  }

  uft.init(n);

  for (int i = m - 1; i >= 0; i--) {
    int u = uft.root(es[i].first), v = uft.root(es[i].second);

    if (u != v) {
      int w = uft.merge(u, v);
      ds[w] = max(ds[u], ds[v]) + 1;
    }
    else
      ds[u]++;
  }

  printf("%d\n", ds[uft.root(0)]);
  return 0;
}