#include <bits/stdc++.h>
#include <random>
using namespace std; typedef unsigned long long _ulong; typedef long long int lint; typedef pair<lint, lint> plint; typedef pair<double long, double long> pld;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(lint i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define endk '\n'
struct fast_ios { fast_ios() { cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(20); }; } fast_ios_;
template<class T> auto add = [](T a, T b) -> T { return a + b; };
template<class T> auto f_max = [](T a, T b) -> T { return max(a, b); };
template<class T> auto f_min = [](T a, T b) -> T { return min(a, b); };
template<class T> using V = vector<T>;
using Vl = V<lint>; using VVl = V<Vl>;
template< typename T > ostream& operator<<(ostream& os, const vector< T >& v) {
	for (int i = 0; i < (int)v.size(); i++) os << v[i] << (i + 1 != v.size() ? " " : "");
	return os;
}
template< typename T >istream& operator>>(istream& is, vector< T >& v) {
	for (T& in : v) is >> in;
	return is;
}
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
lint gcd(lint a, lint b) { if (b == 0) return a; else return gcd(b, a % b); }
lint ceil(lint a, lint b) { return (a + b - 1) / b; }
lint digit(lint a) { return (lint)log10(a); }
lint dist(plint a, plint b) { return abs(a.first - b.first) * abs(a.first - b.first) + abs(a.second - b.second) * abs(a.second - b.second); }
lint m_dist(plint a, plint b) { return abs(a.first - b.first) + abs(a.second - b.second); }
void Worshall_Floyd(VVl& g) { REP(k, SZ(g)) REP(i, SZ(g)) REP(j, SZ(g)) chmin(g[i][j], g[i][k] + g[k][j]); }
const lint MOD = 1e9 + 7, INF = 5e18;
lint dx[8] = { 1, 0, -1, 0, 1, -1, 1, -1 }, dy[8] = { 0, 1, 0, -1, -1, -1, 1, 1 };
bool YN(bool flag) { cout << (flag ? "YES" : "NO") << endk; return flag; } bool yn(bool flag) { cout << (flag ? "Yes" : "No") << endk; return flag; }
struct Edge {
	lint from, to;
	lint cost;
	Edge(lint u, lint v, lint c) {
		cost = c;
		from = u;
		to = v;
	}
	bool operator<(const Edge& e) const {
		return cost < e.cost;
	}
};
struct WeightedEdge {
	lint to;
	lint cost;


	WeightedEdge(lint v, lint c = 1) {
		to = v;
		cost = c;
	}
	bool operator<(const WeightedEdge& e) const {
		return cost < e.cost;
	}
};
using WeightedGraph = V<V<WeightedEdge>>;
typedef pair<plint, lint> tlint;
typedef pair<plint, plint> qlint;
typedef pair<string, lint> valstring;

lint N, M, u, v;
int main() {
	cin >> N >> M;
	VVl mat(N, Vl(N, 0));
	REP(i, M) {
		cin >> u >> v; u--; v--;
		mat[u][v] = 1;
		mat[v][u] = 1;
	}
	Vl dp(1 << N, INF);
	V<plint> vec;
	FOR(mask, 1, 1 << N) {
		bool flag = true;
		REP(i, N) {
			FOR(j, i + 1, N) {
				if (((mask >> i) % 2) && (mask >> j) % 2) {
					if (mat[i][j] == 0) flag = false;
				}
			}
		}
		lint cnt = 0;
		REP(i, N) {
			if ((mask >> i) % 2 == 1) cnt++;
		}
		if (flag) {
			dp[mask] = 1;
		}
		vec.push_back({ cnt, mask });
	}
	sort(ALL(vec));
	for(plint v : vec) {
		lint mask = v.second;
		for (lint bit = mask; ; bit = (bit - 1) & mask) {
			if (!(dp[bit] == INF || dp[mask ^ bit] == INF)) {
				chmin(dp[mask], dp[bit] + dp[mask ^ bit]);
			}
			if (bit == 0) break;
		}
	}
	cout << dp[(1ll << N) - 1] << endk;
}
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int sz = 19, msz = 1 << sz;

int n, m, g[sz][sz], dp[msz];
bitset <msz> can;

int main() {
   cin >> n >> m;
   while(m--) {
      int u, v;
      scanf("%d %d", &u, &v);
      u--, v--;
      g[u][v] = g[v][u] = 1;
   }
   int lim = 1 << n;
   can.set();
   for(int i=1; i<lim; i++) {
      vector <int> nodes;
      for(int j=0; j<n; j++) if(i & (1 << j)) nodes.push_back(j);
      for(int &x : nodes) {
         for(int &y : nodes) {
            if(x ^ y and !g[x][y]) can[i] = 0;
         }
      }
   }

   for(int i=1; i<lim; i++) {
      dp[i] = n;
      for(int j=i; j>0; j=(j-1)&i)
         if(can[j]) dp[i] = min(dp[i], 1 + dp[i ^ j]);
   }
   cout << dp[lim-1];
}