#include <iostream>
using namespace std;
#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
using namespace std;
ifstream fin("graf.in");
int n, m;
vector <int> szint;
vector <int> os;
vector <vector<int>> t;
vector <int> jart;
void be() {
    int a, b;
    cin >> n >> m;
    szint.resize(n + 1);
    os.resize(n + 1);
    t.resize(n + 1);
    jart.resize(n + 1);
    for (int i = 1; i <= m; i++) {
        cin >> a >> b;
        t[a].push_back(b);
        t[b].push_back(a);
    }
    for (int i = 1; i <= n; i++) {
        sort(t[i].begin(), t[i].end());
    }
}
void ki() {
    for (int i = 1; i <= n; i++) {
        cout << i << ": ";
        for (int j = 0; j < t[i].size(); j++) {
            cout << t[i][j] << ' ';
        }
        cout << endl;
    }
}
vector <int> veki;
stack <int> st;
void DFS(int kcs) {

    for (auto x: t[kcs]) {
        if (!jart[x]) {
            st.push(kcs);
            jart[kcs] = 1;
            os[x] = kcs;
            szint[x] = szint[kcs] + 1;
            DFS(x);
        }
        else {
            if (szint[x] < szint[kcs]&&os[kcs]!=x) {
                veki.push_back(szint[kcs] - szint[x]+1);
            }
        }
    }
}
int main()
{
    be();
    //ki();
    szint[1] = 0;
    os[1] = 0;
    st.push(1);
    jart[1] = 1;
    DFS(1);
    int maxx = 0;
    for (int i = 0; i < veki.size(); i++) {
        if (maxx < veki[i]) maxx = veki[i];
    }
    cout << maxx;
}