#include <bits/stdc++.h>
using namespace std;

#ifdef _RUTHEN
#include <debug.hpp>
#else
#define show(...) true
#endif

using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
template <class T> using V = vector<T>;


struct unionfind {
    std::vector<int> parents;

    unionfind() {}
    unionfind(int n) : parents(n, -1) {}

    int leader(int x) { return parents[x] < 0 ? x : parents[x] = leader(parents[x]); }

    bool merge(int x, int y) {
        x = leader(x), y = leader(y);
        if (x == y) return false;
        if (parents[x] > parents[y]) std::swap(x, y);
        parents[x] += parents[y];
        parents[y] = x;
        return true;
    }

    bool same(int x, int y) { return leader(x) == leader(y); }

    int size(int x) { return -parents[leader(x)]; }

    void init(int n) { parents.assign(n, -1); }  // reset
};

/**
 * @brief UnionFind
 * @docs docs/data_structure/unionfind.md
 */

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N, M;
    cin >> N >> M;
    V<int> A(M), B(M);
    rep(i, M) {
        cin >> A[i] >> B[i];
        A[i]--, B[i]--;
    }
    reverse(A.begin(), A.end());
    reverse(B.begin(), B.end());
    V<int> t(N);
    unionfind uf(N);
    rep(i, M) {
        int x = uf.leader(A[i]), y = uf.leader(B[i]);
        int r = max(t[x], t[y]);
        t[x] = t[y] = r + 1;
        uf.merge(A[i], B[i]);
    }
    int ans = *max_element(t.begin(), t.end());
    cout << ans << '\n';
    return 0;
}