#include <bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define Co_mot_su_that_la return

using namespace std;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;
typedef vector<iii> viii;

const int Minh_dep_trai = 0;
const int N = 20;

int q;
int n,m;
vector<int> a[N];
int res = 0;
int mark[N];

int getbit(int pos, int val)
{
    return (val >> (pos-1)) & 1;
}

signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);cout.tie(0);
  q = 1;
  freopen("test.inp","r",stdin);
  while (q--)
  {
    //your code goes here
    cin >> n >> m;
    for(int i=1; i<=m; i++)
    {
        int u,v;
        cin >> u >> v;
        a[u].pb(v);
        a[v].pb(u);
    }
    int nn = (1 << n);
    //cout << nn;
    for(int i = 0; i < nn; i++)
    {
        int turn = __builtin_popcount(i);
        memset(mark, 0, sizeof mark);
        for(int j=1; j<=n; j++)
        {
            if (getbit(j,i))
            {
                mark[j] = 1 - mark[j];
                for(int u = 0; u < a[j].size();u++)
                {
                    int v = a[j][u];
                    mark[v] = 1 - mark[v];
                }
            }
        }
        bool ok = true;
        for(int i=1; i<=n; i++) if (!mark[i]) ok = false;
        if (ok) res = max(res, turn);
    }
    cout << res;
  }
  Co_mot_su_that_la Minh_dep_trai;
}