#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<stack>
#include<queue>
#include<cstring>
#include<deque>
#define maxn 3010
#define itn int
#define xlm mylove
using namespace std;
int f[maxn];int p,n;int temp,temp1,temp2;
bool can[maxn];int r;int t[maxn];int ts=0;
inline int ff(int x){
	if (f[x]==x) return x;
	return f[x]=ff(f[x]);
}
inline bool unionn(int x,int y){
	int fax=ff(x);
	int fay=ff(y);
	if (fax==fay) return true;
	else {
		f[fax]=fay;
		return false;
	}
}
int Main(){
	freopen("salenet.in","r",stdin);
	freopen("salenet.out","w",stdout);
	scanf("%d%d",&n,&p);
	memset(can,0,sizeof(can));
	for (int i=1;i<=p;i++){
		scanf("%d",&temp1,&temp2);
		can[temp1]=1;ts=min(ts,temp2);
	}
	scanf("%d",&r);
	for (int i=1;i<=r;i++){
		scanf("%d%d",&temp1,&temp2);
		if (can[temp1]) can[temp2]=1;
	}
	for (int i=1;i<n;i++){
		if (!can[i]) {
			printf("NO\n%d",i);
			return 0;
		}
	}
	printf("YES\n%d",ts);
	return 0;
}
int main(){;}
int xlm=Main();