#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
#define rep(i, a, b) for(ll i = a; i < b; ++i)
#define rrep(i, a, b) for(ll i = a; i >= b; --i)
constexpr ll inf = 4e18;
struct SetupIO {
    SetupIO() {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout << fixed << setprecision(30);
    }
} setup_io;
struct UnionFind {
    UnionFind(int N)
        : n(N), data(N, -1) {}
    int merge(int a, int b) {
        assert(0 <= a and a < n);
        assert(0 <= b and b < n);
        int x = leader(a), y = leader(b);
        if(x == y) return x;
        if(-data[x] < -data[y]) swap(x, y);
        data[x] += data[y];
        data[y] = x;
        return x;
    }
    bool same(int a, int b) {
        assert(0 <= a and a < n);
        assert(0 <= b and b < n);
        return leader(a) == leader(b);
    }
    int leader(int a) {
        assert(0 <= a and a < n);
        if(data[a] < 0) return a;
        return data[a] = leader(data[a]);
    }
    int size(int a) {
        assert(0 <= a and a < n);
        return -data[leader(a)];
    }
    vector<vector<int>> groups() {
        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]];
        }
        vector<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(remove_if(result.begin(), result.end(), [&](const vector<int>& v) { return v.empty(); }), result.end());
        return result;
    }

   private:
    int n;
    vector<int> data;
};
int main(void) {
    int n, m;
    cin >> n >> m;
    vector<int> u(m), v(m);
    rep(i, 0, m) {
        cin >> u[i] >> v[i];
        u[i]--;
        v[i]--;
    }
    UnionFind uf(n);
    vector<int> ans(n);
    rrep(i, m - 1, 0) {
        if(uf.same(u[i], v[i])) {
            ans[uf.leader(u[i])]++;
        } else {
            int cnt = max(ans[uf.leader(u[i])], ans[uf.leader(v[i])]);
            uf.merge(u[i], v[i]);
            ans[uf.leader(u[i])] = cnt + 1;
        }
    }
    cout << ans[uf.leader(0)] << '\n';
}