//********************************************
//???????????
//??????
//?????2010.12.10
//???????????
//********************************************
int main ()
{
	//??????????????????????????????????count1????????????count2
	int n, a[2], i, num = 0, count1[10000] = {0},count2[10000] ={0};
	cin >> n;
	do
	{
		cin >> a[0] >> a[1];
		if (a[0] ==0 && a[1] == 0)
			break;//??0 0 ?????
		count1[a[0]]++;
		count2[a[1]]++;
	}while(1);
	for ( i = 0; i < n; i++)
	{
		if ( count1[i] == 0 && count2[i] == (n - 1))
		{
			cout << i << endl;//???????????????????????
			num++;//???????1
		}
	}
	if ( num == 0 )
		cout << "NOT FOUND" << endl;//???????????NOT FOUND
	return 0;
}