#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

struct UnionFind{
    vector<ll> parent;
    vector<ll> sizes;
    vector<ll> cnt;
    
    UnionFind(ll N) : parent(N), sizes(N, 1), cnt(N, 0){
        rep(i, N) parent[i] = i;
    }
    
    ll root(ll x){
        if (parent[x] == x) return x;
        return parent[x] = root(parent[x]);
    }
 
    void unite(ll x, ll y){
        ll rx = root(x);
        ll ry = root(y);
        if (rx == ry){
            cnt[rx]++;
            return;
        }
        if (sizes[rx] < sizes[ry]) swap(rx, ry);
        cnt[rx] = max(cnt[rx], cnt[ry])+1;
        sizes[rx] += sizes[ry];
        parent[ry] = rx;
    }
 
    bool same(ll x, ll y){
        ll rx = root(x);
        ll ry = root(y);
        return rx == ry;
    }
 
    ll size(ll x){
        return sizes[root(x)];
    }

    ll count(ll x){
        return cnt[root(x)];
    }
};

int main(){
    ll n, m;
    cin >> n >> m;

    vector<pll> e(m);
    rep(i, m){
        ll u, v;
        cin >> u >> v;
        u--; v--;
        e[i] = {u, v};
    }

    UnionFind UF(n);
    
    for(ll i=m-1; i>=0; i--){
        UF.unite(e[i].fi, e[i].se);
    }

    cout << UF.count(0) << endl;
}