#include <bits/stdc++.h> #include <algorithm> #include <cassert> #include <vector> namespace atcoder { struct dsu { public: dsu() : _n(0) {} explicit dsu(int n) : _n(n), parent_or_size(n, -1) {} int merge(int a, int b) { assert(0 <= a && a < _n); assert(0 <= b && b < _n); int x = leader(a), y = leader(b); if (x == y) return x; if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y); parent_or_size[x] += parent_or_size[y]; parent_or_size[y] = x; return x; } bool same(int a, int b) { assert(0 <= a && a < _n); assert(0 <= b && b < _n); return leader(a) == leader(b); } int leader(int a) { assert(0 <= a && a < _n); if (parent_or_size[a] < 0) return a; return parent_or_size[a] = leader(parent_or_size[a]); } int size(int a) { assert(0 <= a && a < _n); return -parent_or_size[leader(a)]; } std::vector<std::vector<int>> groups() { std::vector<int> leader_buf(_n), group_size(_n); for (int i = 0; i < _n; i++) { leader_buf[i] = leader(i); group_size[leader_buf[i]]++; } std::vector<std::vector<int>> result(_n); for (int i = 0; i < _n; i++) { result[i].reserve(group_size[i]); } for (int i = 0; i < _n; i++) { result[leader_buf[i]].push_back(i); } result.erase( std::remove_if(result.begin(), result.end(), [&](const std::vector<int>& v) { return v.empty(); }), result.end()); return result; } private: int _n; std::vector<int> parent_or_size; }; } // namespace atcoder using namespace std; using namespace atcoder; int main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); int n, m; cin >> n >> m; vector<pair<int, int>> ed; for (int i = 0; i < m; i++) { int u, v; cin >> u >> v; u--; v--; ed.push_back({u, v}); } vector<int> ops(n); dsu d(n); reverse(ed.begin(), ed.end()); for (auto [u, v] : ed) { u = d.leader(u); v = d.leader(v); if (u == v) { ops[u]++; } else { int ans = max(ops[u], ops[v]); d.merge(u, v); ops[d.leader(u)] = ans + 1; } } cout << *max_element(ops.begin(), ops.end()); }