#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 5;

int n, m, dfn[maxn], low[maxn], idx, dcc, id[maxn];
stack<int> stk;
vector<int> g[maxn], G[maxn];

void tarjan(int u, int p) {
    dfn[u] = low[u] = ++idx;
    stk.push(u);
    for (auto v : g[u]) {
        if (v == p) continue;
        if (!dfn[v])
            tarjan(v, u), low[u] = min(low[u], low[v]);
        else
            low[u] = min(low[u], dfn[v]);
    }
    if (dfn[u] == low[u]) {
        dcc++;
        int v;
        do {
            v = stk.top();
            stk.pop();
            id[v] = dcc;
        } while (v != u);
    }
}

void build_new_grapph() {
    set<pair<int, int>> st;
    for (int u = 1; u <= n; u++) {
        for (auto v : g[u]) {
            int uu = id[u], vv = id[v];
            if (uu != vv && !st.count({uu, vv})) {
                st.insert({uu, vv});
                st.insert({vv, uu});
                G[uu].push_back(vv);
                G[vv].push_back(uu);
            }
        }
    }
}

int dis[maxn];

void dfs(int u, int p, int d) {
    dis[u] = d;
    for (auto v : G[u])
        if (v != p)
            dfs(v, u, d+1);
}

int main() {
    scanf("%d%d", &n, &m);
    while (m--) {
        int u, v;
        scanf("%d%d", &u, &v);
        g[u].push_back(v);
        g[v].push_back(u);
    }
    tarjan(1, -1);
//    test();
    build_new_grapph();
    dfs(1, -1, 0);
    int p = 1;
    for (int i = 1; i <= dcc; i++)
        if (dis[i] > dis[p])
            p = i;
//    test2();
    dfs(p, -1, 0);
    int ans = 0;
    for (int i = 1; i <= dcc; i++)
        ans = max(ans, dis[i]);
//    test2();
    printf("%d\n", ans);
    return 0;
}