#include <bits/stdc++.h>
using namespace std;
static inline void canhazfast() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
}
template <typename T>
T gcd(T a, T b) {
  return b == 0 ? a : gcd(b, a % b);
}
template <typename T>
T extgcd(T a, T b, T &x, T &y) {
  T x0 = 1, y0 = 0, x1 = 0, y1 = 1;
  while (b) {
    T q = a / b;
    a %= b;
    swap(a, b);
    x0 -= q * x1;
    swap(x0, x1);
    y0 -= q * y1;
    swap(y0, y1);
  }
  x = x0;
  y = y0;
  return a;
}
static inline int ctz(unsigned x) { return __builtin_ctz(x); }
static inline int ctzll(unsigned long long x) { return __builtin_ctzll(x); }
static inline int clz(unsigned x) { return __builtin_clz(x); }
static inline int clzll(unsigned long long x) { return __builtin_clzll(x); }
static inline int popcnt(unsigned x) { return __builtin_popcount(x); }
static inline int popcntll(unsigned long long x) {
  return __builtin_popcountll(x);
}
static inline int bsr(unsigned x) { return 31 ^ clz(x); }
static inline int bsrll(unsigned long long x) { return 63 ^ clzll(x); }
vector<int> adj[300016];
int id[300016], lo[300016];
int par[300016], rnk[300016], dist[300016];
vector<int> tadj[300016];
vector<pair<int, int> > br;
int nxt = 0;
int fin(int x) { return par[x] == x ? x : par[x] = fin(par[x]); }
void uni(int x, int y) {
  if (rnk[x] < rnk[y]) {
    par[x] = y;
  } else {
    par[y] = x;
    rnk[x] = max(rnk[x], rnk[y] + 1);
  }
}
void dfs(int u, int p = 0) {
  id[u] = lo[u] = ++nxt;
  for (int v : adj[u]) {
    if (!id[v]) {
      dfs(v, u);
      lo[u] = min(lo[u], lo[v]);
      if (lo[v] > id[u]) {
        br.emplace_back(u, v);
      } else {
        int ru = fin(u), rv = fin(v);
        if (ru != rv) uni(ru, rv);
      }
    } else if (v != p) {
      lo[u] = min(lo[u], lo[v]);
    }
  }
}
int bfs(int s, int n) {
  queue<int> q;
  int r = 0;
  fill_n(dist + 1, n, 1010101);
  dist[s] = 0;
  q.push(s);
  while (!q.empty()) {
    int u = q.front();
    q.pop();
    r = u;
    for (int v : tadj[u]) {
      if (dist[u] + 1 < dist[v]) {
        dist[v] = dist[u] + 1;
        q.push(v);
      }
    }
  }
  return r;
}
int main() {
  canhazfast();
  int n, m, t;
  cin >> n >> m;
  for (int i = 1; i <= n; ++i) par[i] = i;
  for (int i = 0; i < m; ++i) {
    int a, b;
    cin >> a >> b;
    adj[a].push_back(b);
    adj[b].push_back(a);
  }
  dfs(1);
  for (pair<int, int> e : br) {
    int a = fin(e.first), b = fin(e.second);
    tadj[a].push_back(b);
    tadj[b].push_back(a);
  }
  t = bfs(fin(1), n);
  t = bfs(t, n);
  cout << dist[t];
  return 0;
}
