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

int main() {
    mt19937 rng(48);
    cout.tie(nullptr)->sync_with_stdio(false);
    int N, M; cin >> N >> M;
    
    array<array<bool, 20>, 20> graph{};
    for (int i = 0; i < M; ++i) {
        int a, b; cin >> a >> b;
        --a, --b;
        graph[a][b] = graph[b][a] = true;
    }

    int mi = N;
    vector<int> S(N), cc(N);
    iota(S.begin(), S.end(), 0);
    for (int it = 0; it <= 25; ++it) {
        shuffle(S.begin(), S.end(), rng);
        int color = 1;
        for (int i = 1; i < N; ++i) {
            int Q = 0;
            for (int j = 0; j < i; ++j) {
                if (!graph[S[j]][S[i]]) Q |= (1 << cc[j]);
            }
            Q ^= (1 << color) - 1;
            if (Q == 0) {
                cc[i] = color++;
            } else {
                while (true) {
                    cc[i] = uniform_int_distribution<int>(0, color + 1)(rng);
                    if (Q & (1 << cc[i])) break;
                }
            }
        }
        mi = min(mi, color);
    }

    cout << mi << '\n';
}

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
template <typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#ifndef aa
#define trace(...)
#define endl '\n'
#endif
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define fi first
#define se second
#define int long long
typedef long long ll;
typedef long double ld;
#define pii pair<int,int>
#define pll pair<ll,ll>
#define sz(x) ((long long)x.size())
#define fr(a,b,c) for(int a=b; a<=c; a++)
#define frev(a,b,c) for(int a=c; a>=b; a--)
#define rep(a,b,c) for(int a=b; a<c; a++)
#define trav(a,x) for(auto &a:x)
#define all(con) con.begin(),con.end()
#define done(x) {cout << x << endl;return;}
#define mini(x,y) x=min(x,y)
#define maxi(x,y) x=max(x,y)
const ll infl = 0x3f3f3f3f3f3f3f3fLL;
const int infi = 0x3f3f3f3f;
mt19937_64 mt(chrono::steady_clock::now().time_since_epoch().count());
//const int mod = 998244353;
const int mod = 1e9 + 7;
typedef vector<int> vi;
typedef vector<string> vs;
typedef vector<vector<int>> vvi;
typedef vector<pair<int, int>> vpii;
typedef map<int, int> mii;
typedef set<int> si;
typedef set<pair<int,int>> spii;
typedef queue<int> qi;
uniform_int_distribution<int> rng(29,1e9);

//DEBUG FUNCTIONS START
#define cerr cout
void __print(int x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
//#define deb(x...) cerr << "[" << #x << "] = "; _print(x)
#define deb(x...)  _print(x)
#else
#define deb(x...)
#endif
// DEBUG FUNCTIONS END







const int N = 2e5+5;



void solve(){
	
	
	int n, m;
	cin >> n >> m;
	
	vvi g(n, vi(n));
	rep(_, 0, m){
		int u, v;
		cin >> u >> v;
		u--, v--;
		g[u][v] = 1;
		g[v][u] = 1;
	}
	
	vi dp(1<<n);
	
	rep(msk,0,1<<n){
		bool ok = 1;
		rep(i,0,n){
			rep(j,i+1,n){
				if((msk >> i & 1) && (msk >> j & 1))
					ok &= (bool)g[i][j];
			}
		}
		
		if(ok){
			dp[msk] = 1;
		}else{
			dp[msk] = infl;
			for(int s = msk; s; s = (s-1) & msk){
				mini(dp[msk], dp[s] + dp[s ^ msk]);
			}
		}
	}
	
	
	cout << dp[(1<<n)-1] << endl;
	
	
}



signed main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cout << fixed << setprecision(10);
    int t = 1;
    //cin >> t;
    while (t--)
        solve();
    return 0;
}


int powm(int a, int b){
    int res = 1;
    while (b) {
        if (b & 1)
            res = (res*a) % mod;
        a = (a * a) % mod;
        b >>= 1;
    }
    return res;
}
 
int divide(int a, int b) {
    return (a % mod) * powm(b % mod, mod - 2) % mod;
}
 
int norm(int a) {
    while (a >= mod) a -= mod;
    while (a < 0) a += mod;
    return a;
}