#include<bits/stdc++.h>
#define x first
#define y second
#define all(x) (x).begin(),(x).end()
#define sz(x) (int)(x).size()
#define mem(x,val) memset(x,val,sizeof x)
#define pii pair<int,int>
#define pb emplace_back
#define ar array
#define int long long
#define FOR(i, a, b) for(int i = a; i < b; i++)
#define M 1000000007
#define wopen(x) freopen((x),"w",stdout)
#define ropen(x) freopen((x),"r",stdin)
using namespace std;
const int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};
const int N = 2e5 + 5;

int n, m, top, chose, dp[(1<<18)], group[(1<<18)], st[20];
bitset<20> mat[20];

void init(){
    for(int i = 0; i < (1<<n); i++){
        top = 0;
        for(int j = 0; j < n; j++)
            if((i>>j)&1) st[top++] = j;
        for(int j = 0; j < top; j++)
            for(int k = 0; k < j; k++)
                if(mat[st[j]][st[k]] == 0)
                    goto next;
        group[i] = 1;
        next:;
    }
}

void dfs(int now, int bit){
    if(group[bit] == 0 && bit) return;
    if(now == top){
        if(group[bit]) dp[chose|bit] = min(dp[chose|bit], dp[chose] + 1);
        return;
    }
    dfs(now + 1, bit | (1<<st[now]));
    dfs(now + 1, bit);
}

signed main(void){
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> n >> m;
    for(int i = 0; i < m; i++){
        int a, b;
        cin >> a >> b;
        a--, b--;
        mat[a][b] = mat[b][a] = 1;
    }
    init();
    mem(dp, 0x3f);
    dp[0] = 0;
    for(int i = 0; i < (1<<n); i++){
        top = 0;
        if(group[i] && i) {
            dp[i] = 1;
        }
        for(int j = 0; j < n; j++)
            if(((i>>j)&1) == 0) st[top++] = j;
        chose = i;
        dfs(0, 0);
    }
    cout << dp[(1<<n)-1];
}

#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define drep(i,j,n) for(int i=0;i<(int)(n-1);i++)for(int j=i+1;j<(int)(n);j++)
#define trep(i,j,k,n) for(int i=0;i<(int)(n-2);i++)for(int j=i+1;j<(int)(n-1);j++)for(int k=j+1;k<(int)(n);k++)
#define codefor int test;scanf("%d",&test);while(test--)
#define INT(...) int __VA_ARGS__;in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;in(__VA_ARGS__)
#define yes(ans) if(ans)printf("yes\n");else printf("no\n")
#define Yes(ans) if(ans)printf("Yes\n");else printf("No\n")
#define YES(ans) if(ans)printf("YES\n");else printf("NO\n")
#define popcount(v) __builtin_popcount(v)
#define vector2d(type,name,h,...) vector<vector<type>>name(h,vector<type>(__VA_ARGS__))
#define vector3d(type,name,h,w,...) vector<vector<vector<type>>>name(h,vector<vector<type>>(w,vector<type>(__VA_ARGS__)))
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD=1000000007;
const int MOD2=998244353;
const int INF=1<<30;
const ll INF2=1LL<<60;
//入力系
void scan(int& a){scanf("%d",&a);}
void scan(long long& a){scanf("%lld",&a);}
template<class T,class L>void scan(pair<T, L>& p){scan(p.first);scan(p.second);}
template<class T,class U,class V>void scan(tuple<T,U,V>& p){scan(get<0>(p));scan(get<1>(p));scan(get<2>(p));}
template<class T> void scan(T& a){cin>>a;}
template<class T> void scan(vector<T>& vec){for(auto&& it:vec)scan(it);}
void in(){}
template <class Head, class... Tail> void in(Head& head, Tail&... tail){scan(head);in(tail...);}
//出力系
void print(const int& a){printf("%d",a);}
void print(const long long& a){printf("%lld",a);}
void print(const double& a){printf("%.15lf",a);}
template<class T,class L>void print(const pair<T, L>& p){print(p.first);putchar(' ');print(p.second);}
template<class T> void print(const T& a){cout<<a;}
template<class T> void print(const vector<T>& vec){if(vec.empty())return;print(vec[0]);for(auto it=vec.begin();++it!= vec.end();){putchar(' ');print(*it);}}
void out(){putchar('\n');}
template<class T> void out(const T& t){print(t);putchar('\n');}
template <class Head, class... Tail> void out(const Head& head,const Tail&... tail){print(head);putchar(' ');out(tail...);}
//デバッグ系
template<class T> void dprint(const T& a){cerr<<a;}
template<class T> void dprint(const vector<T>& vec){if(vec.empty())return;cerr<<vec[0];for(auto it=vec.begin();++it!= vec.end();){cerr<<" "<<*it;}}
void debug(){cerr<<endl;}
template<class T> void debug(const T& t){dprint(t);cerr<<endl;}
template <class Head, class... Tail> void debug(const Head& head, const Tail&... tail){dprint(head);cerr<<" ";debug(tail...);}
ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; }
ll modpow(ll a, ll b, ll p){ ll ans = 1; while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; }
ll modinv(ll a, ll m) {ll b = m, u = 1, v = 0;while (b) {ll t = a / b;a -= t * b; swap(a, b);u -= t * v; swap(u, v);}u %= m;if (u < 0) u += m;return u;}
ll updivide(ll a,ll b){if(a%b==0) return a/b;else return (a/b)+1;}
template<class T> void chmax(T &a,const T b){if(b>a)a=b;}
template<class T> void chmin(T &a,const T b){if(b<a)a=b;}

int main(){
    INT(n,m);
    vector2d(bool,A,n,n,false);
    int u,v;
    rep(i,m){
        in(u,v);
        A[--u][--v]=true;
        A[v][u]=true;
    }
    vector<int> dp(1<<n,0);
    bool h=false;
    rep(S,1<<n){
        dp[S]=popcount(S);
        h=true;
        for(int i=0;i<n;i++){
            if(~S>>i&1)continue;
            for(int j=i+1;j<n;j++){
                if(~S>>j&1)continue;
                if(!A[i][j]){
                    h=false;
                    break;
                }
            }
        }
        if(h){
            dp[S]=1;
            continue;
        }
        for(int T=(S-1)&S;T>0;T=(T-1)&S){
            chmin(dp[S],dp[S^T]+dp[T]);
        }
    }
    out(dp.back());
}