int main()
{
	int n,k,a[1000],count=0;
	cin>>n>>k;
	int i,j;
	for(i=0;i<n;i++)
		cin>>a[i];//???????????
	for(i=0;i<n;i++)
		for(j=i+1;j<n;j++)
		{
			if(a[i]+a[j]!=k)
				count=count+1;
		}//????????????????????k??????
	int m;
	m=n*(n-1)/2;
	if(count<m)
		cout<<"yes"<<endl;
	else
		cout<<"no"<<endl;//???????m??????????
	return 0;

}