/*
TASK:TRI
LANG:C++
*/
#include<iostream>
using namespace std;
bool a[2006][2006];
int main()
{
  int minsum=6000;
	int x,y,i,j,l,n,m;
	cin>>n>>m;
	for(i=1;i<=m;i++)
	{
		cin>>x>>y;
		a[x][y]=1;
		a[y][x]=1;
	}
	for(i=1;i<=n;i++)
	for(j=i+1;j<=n;j++)
	if(a[i][j])
	for(l=j+1;l<=n;l++)
	if(a[j][l] && a[i][l] && i+j+l<minsum)
	minsum=i+j+l;
	if(minsum==6000)
	cout<<0<<endl;
	else cout<<minsum<<endl;
}
