#include <bits/stdc++.h>

using namespace std;

#define rep(i,n) for(int i = 0; i < (int)(n); ++i)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; --i)
#define ALL(a) a.begin(), a.end()
#define Sort(a) sort(a.begin(), a.end())
#define RSort(a) sort(a.rbegin(), a.rend())

typedef long long int ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef vector<char> vc;
typedef vector<string> vst;
typedef vector<double> vd;
typedef pair<long long, long long> P;

const long long INF = 0x1fffffffffffffff;
const long long MOD = 1000000007;
const long double PI = acos(-1);
 
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T, class U> inline T vin(T& vec, U n) { vec.resize(n); for(int i = 0; i < (int) n; ++i) cin >> vec[i]; return vec; }
template<class T> inline void vout(T vec, string s = "\n"){ for(auto x : vec) cout << x << s; }
template<class... T> void in(T&... a){ (cin >> ... >> a); }
void out(){ cout << '\n'; }
template<class T, class... Ts> void out(const T& a, const Ts&... b){ cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; }
template<class T, class U> void inGraph(vector<vector<T>>& G, U n, U m, bool directed = false){ G.resize(n); for(int i = 0; i < m; i++){ int a, b; cin >> a >> b; a--, b--; G[a].push_back(b); if(!directed) G[b].push_back(a); } }

struct UnionFind {
    vector<int> par;
    vector<int> siz;
    vector<int> edg;

    UnionFind(int N) : par(N), siz(N), edg(N) {
        for(int i = 0; i < N; i++){
            par[i] = i;
            siz[i] = 1;
            edg[i] = 0;
        }
    }

    int root(int x) {
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    void unite(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        if (rx == ry){
            edg[rx]++;
            return;
        }
        par[rx] = ry;
        siz[ry] += siz[rx];
        edg[ry] += edg[rx] + 1;
    }

    bool same(int x, int y){
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }

    long long size(int x){
        return siz[root(x)];
    }

    long long edge(int x){
        return edg[root(x)];
    }
};

ll n, m;

void input(){
    in(n, m);
}
 
void solve(){
    ll ans = 0;
    vll cnt(n);
    UnionFind tree(n);
    vector<P> e(m);
    rep(i, m){
        ll a, b; in(a, b); a--; b--;
        e[i] = {a, b};
    }
    reverse(ALL(e));
    rep(i, m){
        ll a = e[i].first, b = e[i].second;
        if(!tree.same(a, b)){
            cnt[tree.root(b)] = max(cnt[tree.root(a)], cnt[tree.root(b)]) + 1;
            tree.unite(a, b);
        }else{
            cnt[tree.root(a)]++; 
        }
    }
    rep(i, n) chmax(ans, cnt[i]);
    out(ans);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    input();
    solve();
}