---

#include <iostream>
#include <vector>
using namespace std;
vector<int> u, v;
int n;
int count(int r)
{
	int res = 0;
	for(int i = 0; i < n; i++)
		if(r & (1 << i))res++;
	return res;
}
int main()
{
	int  m;
	cin >> n >> m;
	u.resize(m);
	v.resize(m);
	for(int i = 0; i < m; i++)
	{
		int a, b;
		cin >> a >> b;
		a--;
		b--;
		u[i] = a;
		v[i] = b;
	}
	vector<int> res(1 << n, -1);
	res[0] = 0;
	int mres = 0;
	for(int i = 1; i < (1 << n); i++)
		if(count(i) % 2 == 0)
		{
			for(int j = 0; j < m; j++)
				if(i & (1 << u[j]) && i & (1 << v[j]))
					res[i] = max(res[i], res[i ^ (1 << u[j]) ^ (1 << v[j])] + 1);
			mres = max(mres, res[i]);
		}
	cout << mres << '\n';
	return 0;
}