#include <bits/stdc++.h>
using namespace std;
char string_in_buffer[(int)260];
void fast_scan(int &first) { scanf("%d", &first); }
void fast_scan(long long &first) { scanf("%lld", &first); }
void fast_scan(unsigned long long &first) { scanf("%llu", &first); }
void fast_scan(double &first) { scanf("%lf", &first); }
void fast_scan(long double &first) { scanf("%Lf", &first); }
void fast_scan(char &first) {
  scanf("%c", &first);
  if (first == '\n') {
    fast_scan(first);
  }
}
void fast_scan(string &first) {
  scanf("%s", string_in_buffer);
  first = string(string_in_buffer);
}
template <class TFirst, class TSecond>
void fast_scan(pair<TFirst, TSecond> &p) {
  fast_scan(p.first);
  fast_scan(p.second);
}
template <class T>
void fast_scan(vector<T> &v) {
  for (auto &first : v) fast_scan(first);
}
void fast_print(const int &first) { printf("%d", first); }
void fast_print(const long long &first) { printf("%lld", first); }
void fast_print(const unsigned long long &first) { printf("%llu", first); }
void fast_print(const double &first) { printf("%.15lf", first); }
void fast_print(const long double &first) { printf("%.15Lf", first); }
void fast_print(const char &first) { printf("%c", first); };
void fast_print(const string &first) { printf("%s", first.c_str()); }
void fast_print(const char v[]) { fast_print((string)v); }
template <class TFirst, class TSecond>
void fast_print(const pair<TFirst, TSecond> &p) {
  fast_print(p.first);
  fast_print(' ');
  fast_print(p.second);
}
template <class T>
void fast_print(const vector<T> &v) {
  if (v.empty()) return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print(' ');
    fast_print(v[i]);
  }
}
template <class T>
void fast_print(const vector<vector<T>> &v) {
  if (v.empty()) return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print('\n');
    fast_print(v[i]);
  }
}
template <class T>
void fast_print(const T &v) {
  for (const auto &first : v) {
    fast_print(first);
    fast_print(' ');
  }
}
using namespace std;
namespace smart_io {
string print_start = "";
string sep = " ";
bool first_print = false;
void precall_print() {
  fast_print(print_start);
  print_start = "\n";
  first_print = true;
}
void _print(deque<string>) {}
template <class T, class... Args>
void _print(deque<string> names, T kek, Args... args) {
  if (!first_print) {
    fast_print("\n");
  } else {
    first_print = false;
  }
  fast_print(names.front());
  fast_print(" = ");
  fast_print(kek);
  names.pop_front();
  _print(names, args...);
}
}  // namespace smart_io
template <class T>
ostream &operator,(ostream &os, const T &object) {
  if (!smart_io::first_print) {
    fast_print(smart_io::sep);
  } else {
    smart_io::first_print = false;
  }
  fast_print(object);
  return os;
}
template <class T>
istream &operator,(istream &is, T &object) {
  fast_scan(object);
  return is;
}
namespace typedefs {}
namespace numbers_operation {
template <class T>
T floor_mod(T a, T b) {
  if (a % b == 0) return 0;
  if (a >= 0 && b >= 0) return a % b;
  if (a <= 0 && b <= 0) return a % b;
  return abs(b) - (abs(a) % abs(b));
}
}  // namespace numbers_operation
using namespace numbers_operation;
using namespace typedefs;
int n, m;
vector<vector<int>> g;
vector<int> tin;
vector<int> uptime;
vector<bool> used;
int timer = 0;
void dfs_time(int v) {
  tin[v] = timer++;
  used[v] = true;
  for (int sub : g[v]) {
    if (used[sub]) continue;
    dfs_time(sub);
  }
}
set<pair<int, int>> bridges;
void dfs(int v, int _p) {
  uptime[v] = tin[v];
  used[v] = true;
  for (int sub : g[v]) {
    if (sub == _p) continue;
    if (!used[sub]) {
      dfs(sub, v);
      if (uptime[sub] > tin[v]) {
        bridges.emplace(v, sub);
        bridges.emplace(sub, v);
      }
    }
    uptime[v] = min(uptime[v], uptime[sub]);
  }
}
vector<int> bfs(int st) {
  vector<int> dist(n, 1e9);
  deque<int> deq{st};
  dist[st] = 0;
  while (!deq.empty()) {
    int v = deq[0];
    deq.pop_front();
    for (int sub : g[v]) {
      if (bridges.count(make_pair(v, sub))) {
        if (dist[sub] > dist[v] + 1) {
          dist[sub] = dist[v] + 1;
          deq.push_back(sub);
        }
      } else {
        if (dist[sub] > dist[v]) {
          dist[sub] = dist[v];
          deq.push_front(sub);
        }
      }
    }
  }
  return dist;
}
signed main(signed argc, char *argv[]) {
  {
    cin, n, m;
    g.resize(n);
  }
  {
    for (int i = 0; i < (m); i++) {
      int a, b;
      cin, a, b;
      a--;
      b--;
      g[a].push_back(b);
      g[b].push_back(a);
    }
  }
  {
    tin.resize(n);
    uptime.resize(n);
  }
  {
    used = vector<bool>(n, false);
    dfs_time(0);
  }
  {
    used = vector<bool>(n, false);
    dfs(0, -1);
  }
  {
    vector<int> dist = bfs(0);
    int far = 0;
    for (int i = 0; i < n; i++) {
      if (dist[i] > dist[far]) {
        far = i;
      }
    }
    dist = bfs(far);
    int rez = 0;
    for (int first : dist) {
      rez = max(rez, first);
    }
    smart_io::precall_print();
    cout, rez;
  }
}
