// Problem: E. We Need More Bosses
// Contest: Codeforces - Educational Codeforces Round 46 (Rated for Div. 2)
// URL: https://codeforces.com/problemset/problem/1000/E
// Memory Limit: 256 MB
// Time Limit: 2000 ms

/*

WINNERS NEVER QUIT AND QUITTERS NEVER WIN!!

Falling down is an accident, Staying down is a choice.

*/
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#include "bits/stdc++.h"
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>*/

using namespace std;
//using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vb> vvb;
typedef vector<vll> vvll;
typedef vector<pll> vpll;
typedef vector<string> vs;
typedef unordered_map<ll,ll> umll;
template<class T> using pq = priority_queue<T, vector<T>, greater<T>>;
/*template <typename num_t>
using ordered_set = tree<num_t, null_type, less<num_t>, rb_tree_tag, tree_order_statistics_node_update>;*/
// find_by_order(k): iterator to the kth largest(0 indexed). order_of_key(k): no. of items < k

#define GET_MACRO(_1,_2,_3,_4,NAME,...) NAME
#define FOR3(i,a,b) for(long long i=a;i<b;i++)
#define FOR4(i,a,b,step) for(long long i=a;i<b;i=i+step)
#define REV3(i,a,b) for(long long i=a;i>=b;i--)
#define REV4(i,a,b,step) for(long long i=a;i>=b;i=i-step)
#define FOR(...) GET_MACRO(__VA_ARGS__, FOR4, FOR3)(__VA_ARGS__)
#define REV(...) GET_MACRO(__VA_ARGS__, REV4, REV3)(__VA_ARGS__)
#define F first
#define S second
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define tc ll tests;cin>>tests;while(tests--)
#define io ios_base::sync_with_stdio(false);cin.tie(nullptr);
#define coutv(v) for(auto it: (v))cout<<it<<" ";newl;
#define cout2d(v) for(auto it: (v)) {for(auto j:it) cout<<j<<" ";newl;}
#define cinv(v,n) vll (v)(n);FOR(i,0,(n)){cin>>v[i];}
#define cinvg(v,n) (v).resize(n);FOR(i,0,(n)){cin>>v[i];}
#define cin2d(v,n,m) vvll (v)(n,vll(m,0));FOR(i,0,n){FOR(j,0,m){cin>>v[i][j];}}
#define cin2dg(v,n,m) (v).resize(n,vll(m));FOR(i,0,n){FOR(j,0,m){cin>>v[i][j];}}
#define pyes(CONDITION) cout << (CONDITION ? "YES" : "NO") << '\n';
#define newl cout<<"\n"
#define MOD 1000000007
#define INF LLONG_MAX/2
#define m1(x) template<class T, class... U> void x(T&& a, U&&... b)
#define m2(x) (int[]){(x forward<U>(b),0)...}
m1(pr) { cout << forward<T>(a);  m2(cout << " " <<); cout << "\n"; }
m1(re) { cin >> forward<T>(a); m2(cin >>); }
template <class ...Args>
auto &readd(Args &...args) { return (cin >> ... >> args); }
#define re(...) __VA_ARGS__; readd(__VA_ARGS__)

const ll dx[4] = {0,1,0,-1}, dy[4] = {1,0,-1,0};
// const ll dx[8] = {-2,-1,1,2,2,1,-1,-2}, dy[8] = {1,2,2,1,-1,-2,-2,-1}; //knight moves

// ************************DEBUG START********************************
// #ifndef ONLINE_JUDGE
// //#define cerr cout
// #include "myprettyprint.hpp"
// #else
// #define dbg(...)
// #endif
// ************************DEBUG END**********************************

constexpr ll pct(ll x) { return __builtin_popcountll(x); } // # of bits set
constexpr ll bits(ll x) {return x == 0LL ? 0LL : 63LL-__builtin_clzll(x); } // floor(log2(x))
constexpr ll p2(ll x) { return 1LL<<x; }
constexpr ll msk2(ll x) { return p2(x)-1LL; }
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

vvll g, adj;
ll bridges = 0, cnt = 0;
vll dp, lev, id;
vb vis;
map<pll, bool> edge;

void dfs(vvll &g, ll u, ll p=-1)
{
    for(auto v:g[u])
    {
        if(lev[v]==0) // edge to child
        {
            lev[v] = lev[u] + 1;
            dfs(g, v, u);
            dp[u] += dp[v];
        }
        else if(lev[v] < lev[u]) // edge up
        {
            dp[u]++;
        }
        else if(lev[v] > lev[u]) // edge down
        {
            dp[u]--;
        }
    }
    dp[u]--; // parent also counted

    if(lev[u]>1 && dp[u]==0)
    {
        bridges++;
        edge[{u,p}] = true;
        edge[{p,u}] = true;
    }
}

void dfs1(ll u)
{
    vis[u] = true;
    id[u] = cnt;
    for(auto v:g[u])
    {
        if(vis[v] || edge.count({u,v})) continue;
        dfs1(v);
    }
}

void test()
{
    ll re(n,m);
    g.resize(n);
    dp.resize(n);
    lev.resize(n);
    id.resize(n);
    vis.resize(n);
    FOR(i,0,m)
    {
        ll re(u,v);
        g[--u].pb(--v);
        g[v].pb(u);
    }

    dfs(g, 0);

    FOR(i,0,n)
    {
        if(!vis[i])
        {
            dfs1(i);
            cnt++;
        }
    }

    adj.resize(cnt);
    FOR(u,0,n)
    {
        for(auto v:g[u])
        {
            if(id[u]!=id[v])
            {
                adj[id[u]].pb(id[v]);
            }
        }
    }

    lev.assign(cnt,0);
    dfs(adj, 0);
    ll u = max_element(all(lev)) - lev.begin();
    lev.assign(cnt,0);
    dfs(adj, u);
    pr(*max_element(all(lev)));
}

int main()
{
    io;
    ll tests=1;
    //cin>>tests;
    while(tests--)
    {
        test();
    }
    return 0;
}