#include<bits/stdc++.h>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<int> vi;
typedef vector<ll> vll;

#define PI (2*acos(0.0))
#define eps 1e-9
#define pb push_back
#define endl "\n"
#define watch(x) cout << (#x) << " is " << (x) << endl;
#define show(v) for(int fi = 0; fi < v.size(); fi++) cout << v[fi] << " "; cout << endl;
#define showpair(v) for(int fi = 0; fi < v.size(); fi++) cout << v[fi].first << " " << v[fi].second << endl;
#define ff first
#define ss second
#define fu cout << "lol" << endl;
#define precision(n) cout << fixed << setprecision(n);
#define lb lower_bound
#define up upper_bound
#define all(a) a.begin(), a.end()
#define min3(a,b,c) min(a,min(b,c))
#define max3(a,b,c) max(a,max(b,c))
#define mem(a,val) memset(a,val,sizeof(a))
#define TC ull T; cin>>T; while(T--)
#define IN(x) {scanf("%d",&x);}
#define LL(x) {scanf("%lld",&x);}
#define CC(x) {scanf("%c",&x);}
#define pfl(x) printf("%d\n",x)
#define pfll(x) printf("%lld\n",x)
#define newl puts("")
#define space printf(" ")
#define MOD 1000000007
#define speed ios_base::sync_with_stdio(false); cin.tie(NULL);
#define ar array

/*

*/

const int N = (1<<20);
int n, m;
int adj[20][20], dp[N];
bool ok[N];

int INF = 1e9;

void solve(){
    cin>>n>>m;
    for(int i = 0; i < m; i++){
        int a, b; cin>>a>>b; a--, b--;
        adj[a][b] = 1;
    }
    for(int mask = 0; mask < 1<<n; mask++){
        ok[mask] = true;
        for(int i = 0; i < n; i++){
            if(mask >> i & 1){
                for(int j = i+1; j < n; j++){
                    if(mask >> j & 1) ok[mask] &= adj[i][j];
                }
            }
        }
    }
    for(int mask = 0; mask < 1<<n; mask++){
        dp[mask] =  ok[mask]? 1 : INF;
        for(int sub = (mask-1)&mask; sub; sub = (sub-1)&mask){
            dp[mask] = min(dp[mask], dp[sub] + dp[ mask^sub ]);
        }
    }
    cout << dp[ (1<<n)-1 ] << endl;
}

int main()
{
    solve();
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<int>;
using VL = vector<ll>;
using VS = vector<string>;
template<class T> using PQ = priority_queue<T, vector<T>, greater<T>>;
#define FOR(i,a,n) for(int i=(a);i<(n);++i)
#define eFOR(i,a,n) for(int i=(a);i<=(n);++i)
#define rFOR(i,a,n) for(int i=(n)-1;i>=(a);--i)
#define erFOR(i,a,n) for(int i=(n);i>=(a);--i)
#define SORT(a) sort(a.begin(),a.end())
#define rSORT(a) sort(a.rbegin(),a.rend())
#define fSORT(a,f) sort(a.begin(),a.end(),f)
#define all(a) a.begin(),a.end()
#define out(y,x) ((y)<0||h<=(y)||(x)<0||w<=(x))
#define tp(a,i) get<i>(a)
#ifdef _DEBUG
#define line cout << "-----------------------------\n"
#define stop system("pause")
#define debug(x) print(x)
#endif
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 60;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10;
constexpr ld pi = 3.1415926535897932;
template<class T>inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, vector<T>& v) { for (auto& a : v)is >> a; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline vector<T> vec(size_t a) { return vector<T>(a); }
template<class T>inline vector<T> defvec(T def, size_t a) { return vector<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return vector<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return vector<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }
template<class T>inline void print(const T& a) { cout << a << "\n"; }
template<class T, class... Ts>inline void print(const T& a, const Ts&... ts) { cout << a << " "; print(ts...); }
template<class T>inline void print(const vector<T>& v) { for (int i = 0; i < v.size(); ++i)cout << v[i] << (i == v.size() - 1 ? "\n" : " "); }
template<class T>inline void print(const vector<vector<T>>& v) { for (auto& a : v)print(a); }
inline string reversed(const string& s) { string t = s; reverse(all(t)); return t; }
template<class T>inline T sum(const vector<T>& a, int l, int r) { return a[r] - (l == 0 ? 0 : a[l - 1]); }
template<class T>inline void END(T s) { print(s); exit(0); }
void END() { exit(0); }

int main() {
    init();

    int n, m; cin >> n >> m;
    auto e = vec<bool>(n, n);
    FOR(i, 0, m) {
        int a, b; cin >> a >> b;
        --a, --b;
        e[a][b] = e[b][a] = true;
    }

    vector<bool> ok(1 << n, true);
    FOR(bit, 0, 1 << n)FOR(i, 0, n)if (bit & (1 << i))FOR(j, i + 1, n) {
        if (bit & (1 << j))ok[bit] = ok[bit] && e[i][j];
    }

    auto dp = defvec<int>(INF, 1 << n);
    FOR(bit, 0, 1 << n) {
        if (ok[bit])dp[bit] = 1;
        for (int sub = bit; sub >= 0; --sub) {
            sub &= bit;
            int bus = bit ^ sub;
            if (ok[sub] && ok[bus])chmin(dp[bit], 2);
            chmin(dp[bit], dp[sub] + dp[bus]);
        }
    }
    print(dp[(1 << n) - 1]);

    return 0;
}