#include <bits/stdc++.h>
#include <stdio.h>

#define __Shibae__      signed main()
#define IOS             ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define fiopen(Path)    freopen(Path".INP", "r", stdin); freopen(Path".OUT", "w", stdout);
#define fipen(Path)     freopen(Path".INP", "r", stdin);
#define sz(s)           (int)s.size()
#define all(x)          x.begin(), x.end()
#define maxHeap         priority_queue<int>
#define minHeap         priority_queue<int, vector<int>, greater<int>>
#define getBit(x, k)    (((x) >> (k)) & 1)
#define MASK(i)         (1LL << (i))
#define SQR(x)          (1LL * ((x) * (x)))
#define db              double
#define ld              long double
#define ui              unsigned int
#define ll              long long
#define ii              pair<int, int>
#define pli             pair<ll, int>
#define pil             pair<int, ll>
#define pll             pair<ll, ll>
#define fi              first
#define se              second

#define FOR(i, a, b)    for(int i = a, _b = b; i <= _b; i += 1)
#define FOD(i, a, b)    for(int i = a, _b = b; i >= _b; i -= 1)
#define REP(i, a)       for(int i = 0, _a = a; i < _a; i++)
#define pb              push_back
#define fau(u, a)       for(auto &u : a)
#define debug           return cout << "debug", void();

using namespace std;

const ll mod = 1e9 + 7;
const int INF = 1e9 + 7;
const ll INFLL = (ll)2e18 + 7LL;
const ld PI = acos(-1);
const int MAX = 5e5+5;
 
const int dx[] = {1, -1, 0, 0, -1, 1, 1, -1};
const int dy[] = {0, 0, 1, -1, -1, -1, 1, 1};

mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());

ll Rand(ll l, ll r) 
{
    return uniform_int_distribution<ll>(l, r)(rd);
}

template<class SHIBA, class ENGINE>
    bool minimize(SHIBA &x, const ENGINE y)
    {
        if(x > y)
        {
            x = y;
            return true;
        } 
        else return false;
    }
template<class SHIBA, class ENGINE>
    bool maximize(SHIBA &x, const ENGINE y)
    {
        if(x < y)
        {
            x = y;
            return true;
        }
        else return false;
    }


/* Template by: Nguyen Nhat Anh from Luong Van Chanh High School for the gifted */
/* From Min Tuoi with love */
        /**       TRY HARD        **/
        /**          ORZ          **/

/* -----------------[ MAIN CODE ]----------------- */

int n, m;
vector<ii> g[MAX];
vector<int> adj[MAX];
int num[MAX], low[MAX], timer;
int cmp[MAX], cnt;
stack<int> st;
bool vis[MAX];

void input()
{
    cin >> n >> m;

    FOR(i, 1, m)
    {
        int u, v; cin >> u >> v;
        g[u].pb({v, i});
        g[v].pb({u, i});
    }
}

void dfs(int u, int pre)
{
    num[u] = low[u] = ++timer;
    st.push(u);
    for (auto [v, id] : g[u])
    {
        if (id == pre) continue;
        if (num[v]) low[u] = min(low[u], num[v]);
        else
        {
            dfs(v, id);
            low[u] = min(low[u], low[v]);
        }
    }
    if (num[u] == low[u])
    {
        ++cnt;
        int v = -36;
        while(v != u)
        {
            v = st.top();
            cmp[v] = cnt;
            num[v] = low[v] = n+1;
            st.pop();
        }
    }
}

ii dfss(int u, int pre)
{
    ii res = {0, u};
    fau(v, adj[u])
    {
        if (v == pre) continue;
        ii tmp = dfss(v, u);
        tmp.fi++;
        maximize(res, tmp);
    }
    return res;
}

void mark(int u, int pre)
{
    vis[u] = 1;
    fau(v, adj[u])
    {
        if (v == pre) continue;
        mark(v, u);
    }
}

int get(int root)
{
    mark(root, -1);
    ii tt = dfss(root, -1);

   return dfss(tt.se, -1).fi;
}

void solve()
{
    FOR(i, 1, n) if (!num[i]) dfs(i, -1);
    FOR(i, 1, n)
    {
        for (auto [v, id] : g[i])
        {
            if (cmp[i] != cmp[v])
            {
                adj[cmp[i]].pb(cmp[v]);
            }
        }
    }
    FOR(i, 1, cnt) 
    {
        sort(all(adj[i]));
        adj[i].resize(unique(all(adj[i])) - adj[i].begin());
    }
    int res = 0;
    FOR(i, 1, cnt) if (!vis[i]) maximize(res, get(i));
    cout << res;
}

__Shibae__
{
    IOS

    const bool multitest = 0;
    int tt = 1; if(multitest) cin >> tt;
 
    while( tt-- ){
        input();
        solve();
        if(tt) cout << "\n";
    }
 
    return 0;
}