#include <bits/stdc++.h>
long long dx[4] = {0, -1, 0, 1};
long long dy[4] = {1, 0, -1, 0};
using namespace std;
class pa3 {
 public:
  long long x, y, z;
  pa3(long long x = 0, long long y = 0, long long z = 0) : x(x), y(y), z(z) {}
  bool operator<(const pa3 &p) const {
    if (x != p.x) return x < p.x;
    if (y != p.y) return y < p.y;
    return z < p.z;
  }
  bool operator>(const pa3 &p) const {
    if (x != p.x) return x > p.x;
    if (y != p.y) return y > p.y;
    return z > p.z;
  }
  bool operator==(const pa3 &p) const {
    return x == p.x && y == p.y && z == p.z;
  }
  bool operator!=(const pa3 &p) const {
    return !(x == p.x && y == p.y && z == p.z);
  }
};
class pa4 {
 public:
  double x;
  long long y, z, w;
  pa4(double x = 0, long long y = 0, long long z = 0, long long w = 0)
      : x(x), y(y), z(z), w(w) {}
  bool operator<(const pa4 &p) const {
    if (x != p.x) return x < p.x;
    if (y != p.y) return y < p.y;
    if (z != p.z) return z < p.z;
    return w < p.w;
  }
  bool operator>(const pa4 &p) const {
    if (x != p.x) return x > p.x;
    if (y != p.y) return y > p.y;
    if (z != p.z) return z > p.z;
    return w > p.w;
  }
  bool operator==(const pa4 &p) const {
    return x == p.x && y == p.y && z == p.z && w == p.w;
  }
};
class pa2 {
 public:
  long long x, y;
  pa2(long long x = 0, long long y = 0) : x(x), y(y) {}
  pa2 operator+(pa2 p) { return pa2(x + p.x, y + p.y); }
  pa2 operator-(pa2 p) { return pa2(x - p.x, y - p.y); }
  bool operator<(const pa2 &p) const { return y != p.y ? y < p.y : x < p.x; }
  bool operator>(const pa2 &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const pa2 &p) const {
    return abs(x - p.x) == 0 && abs(y - p.y) == 0;
  }
  bool operator!=(const pa2 &p) const {
    return !(abs(x - p.x) == 0 && abs(y - p.y) == 0);
  }
};
class Point {
 public:
  double x, y;
  Point(double x = 0, double y = 0) : x(x), y(y) {}
  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(x * a, y * a); }
  Point operator/(double a) { return Point(x / a, y / a); }
  double absv() { return sqrt(norm()); }
  double norm() { return x * x + y * y; }
  bool operator<(const Point &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const Point &p) const {
    return fabs(x - p.x) < (1e-10) && fabs(y - p.y) < (1e-10);
  }
};
struct Segment {
  Point p1, p2;
};
double dot(Point a, Point b) { return a.x * b.x + a.y * b.y; }
double cross(Point a, Point b) { return a.x * b.y - a.y * b.x; }
bool parareru(Point a, Point b, Point c, Point d) {
  return abs(cross(a - b, d - c)) < (1e-10);
}
double distance_ls_p(Point a, Point b, Point c) {
  if (dot(b - a, c - a) < (1e-10)) return (c - a).absv();
  if (dot(a - b, c - b) < (1e-10)) return (c - b).absv();
  return abs(cross(b - a, c - a)) / (b - a).absv();
}
bool is_intersected_ls(Segment a, Segment b) {
  if (a.p1 == b.p1 || a.p2 == b.p1 || a.p1 == b.p2 || a.p2 == b.p2)
    return false;
  if (parareru((a.p2), (a.p1), (a.p1), (b.p2)) &&
      parareru((a.p2), (a.p1), (a.p1), (b.p1))) {
    if (dot(a.p1 - b.p1, a.p1 - b.p2) < (1e-10)) return true;
    if (dot(a.p2 - b.p1, a.p2 - b.p2) < (1e-10)) return true;
    if (dot(a.p1 - b.p1, a.p2 - b.p1) < (1e-10)) return true;
    if (dot(a.p1 - b.p2, a.p2 - b.p2) < (1e-10)) return true;
    return false;
  } else
    return (cross(a.p2 - a.p1, b.p1 - a.p1) * cross(a.p2 - a.p1, b.p2 - a.p1) <
            (1e-10)) &&
           (cross(b.p2 - b.p1, a.p1 - b.p1) * cross(b.p2 - b.p1, a.p2 - b.p1) <
            (1e-10));
}
double segment_dis(Segment a, Segment b) {
  if (is_intersected_ls(a, b)) return 0;
  double r = distance_ls_p(a.p1, a.p2, b.p1);
  r = min(r, distance_ls_p(a.p1, a.p2, b.p2));
  r = min(r, distance_ls_p(b.p1, b.p2, a.p2));
  r = min(r, distance_ls_p(b.p1, b.p2, a.p1));
  return r;
}
Point intersection_ls(Segment a, Segment b) {
  Point ba = b.p2 - b.p1;
  double d1 = abs(cross(ba, a.p1 - b.p1));
  double d2 = abs(cross(ba, a.p2 - b.p1));
  double t = d1 / (d1 + d2);
  return a.p1 + (a.p2 - a.p1) * t;
}
string itos(long long i) {
  ostringstream s;
  s << i;
  return s.str();
}
long long gcd(long long v, long long b) {
  if (v > b) return gcd(b, v);
  if (v == b) return b;
  if (b % v == 0) return v;
  return gcd(v, b % v);
}
double distans(double x1, double y1, double x2, double y2) {
  double rr = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  return sqrt(rr);
}
long long mod;
long long pr[50010];
long long inv[50010];
long long beki(long long wa, long long rr, long long warukazu) {
  if (rr == 0) return 1 % warukazu;
  if (rr == 1) return wa % warukazu;
  if (rr % 2 == 1) return (beki(wa, rr - 1, warukazu) * wa) % warukazu;
  long long zx = beki(wa, rr / 2, warukazu);
  return (zx * zx) % warukazu;
}
long long comb(long long nn, long long rr) {
  long long r = pr[nn] * inv[rr];
  r %= mod;
  r *= inv[nn - rr];
  r %= mod;
  return r;
}
void gya(long long ert) {
  pr[0] = 1;
  for (long long i = 1; i < ert; i++) {
    pr[i] = (pr[i - 1] * i) % mod;
  }
  for (long long i = 0; i < ert; i++) inv[i] = beki(pr[i], mod - 2, mod);
}
set<pair<long long, long long> > hasi;
long long pre[300100], lowlink[300100];
vector<long long> G[300100];
long long counter_hasi = 1;
void dfs_hasi(long long r, long long mae, vector<long long> *graph) {
  if (pre[r] >= 0) return;
  pre[r] = counter_hasi;
  counter_hasi++;
  long long f = pre[r];
  long long oyacnt = 0;
  for (long long i = 0; i < graph[r].size(); i++) {
    if (graph[r][i] == mae) {
      oyacnt++;
      if (oyacnt == 1) continue;
    }
    if (pre[graph[r][i]] < 0) {
      dfs_hasi(graph[r][i], r, graph);
      f = min(f, lowlink[graph[r][i]]);
      if (pre[graph[r][i]] == lowlink[graph[r][i]]) {
        if (r < graph[r][i])
          hasi.insert(make_pair(r, graph[r][i]));
        else
          hasi.insert(make_pair(graph[r][i], r));
      }
    } else {
      f = min(f, pre[graph[r][i]]);
    }
  }
  lowlink[r] = f;
  return;
}
void hashi_kenshutu(long long V, vector<long long> *graph) {
  for (long long i = 0; i <= V; i++) pre[i] = -1, lowlink[i] = -1;
  counter_hasi = 1;
  for (long long i = 0; i < V; i++) {
    if (pre[i] == -1) dfs_hasi(i, i, graph);
  }
  return;
}
bool sumi[300020] = {0};
long long num[300020] = {0};
void dfs(long long r, long long p, long long moto) {
  if (sumi[r]) return;
  sumi[r] = 1;
  num[r] = moto;
  for (auto v : G[r]) {
    if (v == p) continue;
    if (r < v) {
      if (hasi.find(make_pair(r, v)) != hasi.end()) continue;
    }
    if (r > v) {
      if (hasi.find(make_pair(v, r)) != hasi.end()) continue;
    }
    dfs(v, r, moto);
  }
}
vector<long long> G2[300020];
long long dis[300020];
long long sai = 0;
void dfs2(long long r, long long p, long long ky) {
  dis[r] = ky;
  if (dis[r] > dis[sai]) sai = r;
  for (auto v : G2[r])
    if (v != p) dfs2(v, r, ky + 1);
}
long long ans = 0;
void dfs3(long long r, long long p, long long ky) {
  if (ans < ky) ans = ky;
  for (auto v : G2[r])
    if (v != p) dfs3(v, r, ky + 1);
}
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  long long n, m;
  cin >> n >> m;
  for (long long i = 0; i < m; i++) {
    long long y, yy;
    cin >> y >> yy;
    y--;
    yy--;
    G[y].push_back(yy);
    G[yy].push_back(y);
  }
  hashi_kenshutu(n, G);
  for (long long i = 0; i < n; i++) {
    if (sumi[i]) continue;
    dfs(i, i, i);
  }
  for (auto it = hasi.begin(); it != hasi.end(); it++) {
    long long y = num[(*it).first];
    long long yy = num[(*it).second];
    G2[y].push_back(yy);
    G2[yy].push_back(y);
  }
  dfs2(0, 0, 0);
  dfs3(sai, sai, 0);
  cout << ans << endl;
  return 0;
}
