#include <bits/stdc++.h>
#include <array>
using namespace std;

typedef long long ll;

// DFS Tree
// Finds bridges, articulation points, and biconnected components
struct DFSTree {
    // size of graph
    int N;
    vector<vector<int>> adj, tree_children, back_edges;
    vector<int> tree_parent;
    vector<int> depth, dp;

    vector<pair<int, int>> bridges;
    vector<int> articulation_points;
    vector<vector<pair<int, int>>> biconnected_components;
    stack<pair<int, int>> edge_stack;

    DFSTree() { DFSTree(0); }
    DFSTree(int _N) : N(_N), adj(_N + 1), tree_children(_N + 1), back_edges(_N + 1), tree_parent(_N + 1, -1), depth(_N + 1, -1), dp(_N + 1) {}

    void add_edge(int u, int v) {
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    void dfs(int curr_node, int curr_depth = 0) {
        depth[curr_node] = curr_depth;
        int cnt = 0;
        for (int next_node : adj[curr_node]) {
            if (next_node == tree_parent[curr_node]) {
                continue;
            }
            if (depth[next_node] == -1) {
                edge_stack.push(make_pair(min(curr_node, next_node), max(curr_node, next_node)));
                tree_children[curr_node].push_back(next_node);
                tree_parent[next_node] = curr_node;
                int curr_dp = dp[curr_node];
                dfs(next_node, curr_depth + 1);
                dp[curr_node] += dp[next_node];
                if (dp[curr_node] == curr_dp) {
                    ++cnt;
                    // separate biconnected component
                    vector<pair<int, int>> component;
                    auto reference_pair = make_pair(min(curr_node, next_node), max(curr_node, next_node));
                    while (true) {
                        auto edge = edge_stack.top();
                        edge_stack.pop();
                        component.push_back(edge);
                        if (edge == reference_pair) {
                            break;
                        }
                    }
                    biconnected_components.push_back(component);
                }
            }
            else if (depth[next_node] < depth[curr_node]) {
                edge_stack.push(make_pair(min(curr_node, next_node), max(curr_node, next_node)));
                back_edges[curr_node].push_back(next_node);
                ++dp[next_node];
                --dp[curr_node];
            }
        }
        if (tree_parent[curr_node] != -1 && dp[curr_node] == 0) {
            bridges.push_back({min(curr_node, tree_parent[curr_node]), max(curr_node, tree_parent[curr_node])});
        }
        if ((tree_parent[curr_node] == -1 && cnt >= 2) || (tree_parent[curr_node] != -1 && cnt >= 1)) {
            articulation_points.push_back(curr_node);
        }
    }

    void compute() {
        for (int i = 1; i <= N; i++) {
            if (depth[i] == -1) {
                dfs(i, 0);
            }
        }
        sort(bridges.begin(), bridges.end());
        sort(articulation_points.begin(), articulation_points.end());
    }
};

// Disjoint set union
struct DSU {
    // size of graph
    int N;
    vector<int> rank;

    DSU() { DSU(0); }
    DSU(int _N) : N(_N), rank(_N + 1, -1) {}

    int get_parent(int node) {
        if (rank[node] < 0) {
            return node;
        }
        return rank[node] = get_parent(rank[node]);
    }

    void merge(int node1, int node2) {
        node1 = get_parent(node1);
        node2 = get_parent(node2);

        if (node1 == node2) return;

        if (-rank[node1] < -rank[node2]) swap(node1, node2);
        rank[node1] += rank[node2];
        rank[node2] = node1;
    }
};

int N, M;

DFSTree tree;
DSU dsu;

vector<int> bridge_dp;

set<pair<int, int>> multiple_edges;
map<pair<int, int>, int> counter;

int ans;

int dfs_dp(int node) {
    // bridge_dp[node] = (tree.tree_parent[node] != -1 && tree.dp[node] == 0);
    // if (tree.tree_parent[node] != -1 && multiple_edges.find({min(node, tree.tree_parent[node]), max(node, tree.tree_parent[node])}) != multiple_edges.end()) {
    //     bridge_dp[node] = 0;
    // }
    vector<int> values;
    for (auto child : tree.tree_children[node]) {
        int curr_val = dfs_dp(child);
        // if (multiple_edges.find({min(node, child), max(node, child)}) == multiple_edges.end() && tree.dp[child] == 0) {
        //     ++curr_val;
        // }
        values.push_back(curr_val);
    }
    sort(values.begin(), values.end());
    if (values.size() == 0) {
        return (tree.tree_parent[node] != -1 && tree.dp[node] == 0 && multiple_edges.find({min(node, tree.tree_parent[node]), max(node, tree.tree_parent[node])}) == multiple_edges.end());
    }
    if (values.size() == 1) {
        ans = max(values[0], ans);
    }
    if (values.size() >= 2) {
        ans = max(values[values.size() - 2] + values[values.size() - 1], ans);
    }
    return values[values.size() - 1] + (tree.tree_parent[node] != -1 && tree.dp[node] == 0 && multiple_edges.find({min(node, tree.tree_parent[node]), max(node, tree.tree_parent[node])}) == multiple_edges.end());
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> N >> M;

    bridge_dp.resize(N + 1);
    dsu = DSU(N);
    tree = DFSTree(N);

    for (int i = 0; i < M; ++i) {
        int u, v;
        cin >> u >> v;
        if (u == v) continue;
        ++u; ++v;
        if (u > v) swap(u, v);
        // tree.add_edge(u, v);
        // edge_sets.insert({u, v});
        ++counter[{u, v}];
        if (counter[{u, v}] == 2) {
            multiple_edges.insert({u, v});
        }
    }
    
    for (auto [p, c] : counter) {
        auto [u, v] = p;
        tree.add_edge(u, v);
    }

    vector<int> parents;
    for (int i = 1; i <= N; ++i) {
        parents.push_back(dsu.get_parent(i));
    }

    sort(parents.begin(), parents.end());
    parents.erase(unique(parents.begin(), parents.end()), parents.end());

    for (int i = 0; i < parents.size() - 1; ++i) {
        tree.add_edge(min(parents[i], parents[i + 1]), max(parents[i], parents[i + 1]));
    }

    tree.compute();

    dfs_dp(1);

    cout << ans << "\n";

    return 0;
}