/*
TASK: TRI
LANG: C++
*/
#include<iostream>
#include<vector>
using namespace std;
int n,m,i,k,j,g,a[2001][2001],p;
vector<int> v[2001];
int main()
{
	scanf("%d%d",&n,&m);
	for(i=0;i<m;i++)
	{
		scanf("%d%d",&k,&p);
		v[k].push_back(p);
		v[p].push_back(k);
		a[k][p]=a[p][k]=1;
	}
	k=10000000;
	for(i=1;i<=n;i++)
	{
		for(j=0;j<v[i].size();j++)
		{
			for(g=0;g<v[v[i][j]].size();g++)
			{
				if(a[i][v[v[i][j]][g]])
				{
					if(i+v[i][j]+v[v[i][j]][g]<k)k=i+v[i][j]+v[v[i][j]][g];
				}
			}
		}
	}
	if(k==10000000)cout<<"0\n";
	else cout<<k<<"\n";
    return 0;
}
