#include <bits/stdc++.h>

using namespace std;

const int INF = 1e9;

vector<vector<int> > adj;
vector<int> dist;
bool vis[10000] = {0};
int ans = 0;

void dfs(int v) {
    vis[v] = 1;

    for(int u : adj[v]) {
        if(!vis[u]) {
            dist[u] = dist[v] + 1;
            dfs(u);
        } else {
            ans = max(ans, abs(dist[u] - dist[v] + 1));
        }
    }

    return;
}

int main() {
    int n, m;
    cin >> n >> m;
    adj.assign(n+1, {});
    dist.assign(n+1, 0);
    for(int i = 1; i <= m; i++) {
        int x, y;
        cin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    for(int i = 1; i <= n; i++) {
        if (!vis[i]) {
            dfs(i);
        }
    }

    cout << ans << endl;

    return 0;
}