#include<stdio.h>
int main()
{
	int n,k;
	scanf("%d%d",&n,&k);
	int x[100],y[100],i;
	for(i=0;i<k;i++)
		scanf("%d%d",&x[i],&y[i]);
	int x1,y1;
	scanf("%d%d",&x1,&y1);
	int flag=0;
	for(i=0;i<k;i++)
	{
		if(x1==x[i]||x1==y[i])
		{
			flag=1;
				break;
		}
	}
	if(flag==1)
		for(i=0;i<k;i++)
			{
			if(y1==x[i]||y1==y[i])
			{
				flag=2;
					break;
			}
		}
	if(flag==2)
		printf("YES\n");
	else
		printf("NO\n");
	return 0;
}
/**************************************************************
	Problem: 2156
	User: admin
	Language: C
	Result: Accepted
	Time:9 ms
	Memory:1144 kb
****************************************************************/