#include <bits/stdc++.h>
#define fst first
#define snd second
#define fore(i,a,b) for(int i=a,ThxDem=b;i<ThxDem;++i)
#define pb push_back
#define ALL(s) s.begin(),s.end()
#define FIN ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define SZ(s) int(s.size())
using namespace std;
typedef long long ll;
typedef pair<int,int> ii;

const int MAXN=1e5+10;
vector<int> g[MAXN];

int main(){FIN;
	int n,m; cin>>n>>m;
	fore(i,0,n){
		int x,y; cin>>x>>y;
	}
	
	fore(i,0,m){
		int x,y; cin>>x>>y; x--; y--;
		g[x].pb(y); g[y].pb(x);
	}
	
	fore(i,0,n) sort(ALL(g[i]));
	
	int can=5;
	
	fore(x,0,n) for(auto y:g[x]) if(SZ(g[x]) >= SZ(g[y])){
		for(auto z:g[y]){
			auto it=lower_bound(ALL(g[z]),x);
			if(it!=g[z].end() && *it==x){
				cout<<"3\n";
				exit(0);
			}
		}
	}
	
	vector<int> vis(n);
	fore(x,0,n){
		for(auto y:g[x]) vis[y]=1;
		
		for(auto y:g[x]) if(SZ(g[x]) >= SZ(g[y])){
			for(auto z:g[y]) if(z!=x && SZ(g[x])>=SZ(g[z])){
				int tot=0;
				for(auto k:g[z]) if(k!=y&&vis[k]){
					cout<<"4\n";
					exit(0);
				}
			}
		}
		
		for(auto y:g[x]) vis[y]=0;
	}
	
	cout<<"5\n";
}