#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for (int i = 0; i < n; i++)
#define rrep(i,n) for (int i = (n) - 1; i >= 0; i--)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}

struct UnionFind {
    vector<int> par, siz;
    UnionFind(int n) : par(n,-1), siz(n,1) {}
    int find(int x){
        if (par[x] == -1) return x;
        else{
            par[x] = find(par[x]);
            return par[x];
        }
    }
    bool same(int x, int y){
        return find(x) == find(y);
    }
    int size(int x){
        return siz[find(x)];
    }
    void unite(int x, int y){
        x = find(x);
        y = find(y);
        if (x == y) return;
        if (siz[x] < siz[y]) swap(x,y);
        siz[x] += siz[y];
        par[y] = x;
    }
};

int n, m;
vector<int> g[200010];

int main(){
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    cin >> n >> m;
    vector<pair<int, int>> vp;
    rep(i, m){
        int u, v;
        cin >> u >> v;
        u--;
        v--;
        vp.push_back(make_pair(u, v));
    }
    reverse(all(vp));
    UnionFind uf(n);
    vector<int> d(n);
    for (auto [u, v] : vp){
        int eu = uf.find(u), ev = uf.find(v);
        if (uf.same(u, v)){
            d[eu]++;
        } else{
            int pu = d[eu], pv = d[ev];
            d[eu] = d[ev] = 0;
            uf.unite(u, v);
            d[uf.find(u)] = max(pu, pv) + 1;
        }
    }
    int ans = 0;
    rep(i, n){
        chmax(ans, d[i]);
    }
    cout << ans << "\n";
}