int main()
{
	int n, a[100000][2], i = 0, j = 0, k, b[100000] = {0}, count[100000] = {0}, t = 0;
	cin >> n;
	do
	{
		cin >> a[i][0] >> a[i][1];
		i++;
	}
	while(a[i - 1][0] != 0 || a[i - 1][1] != 0);        //????????????0
	k = i - 1;                                  //?????????
	for(i = 0; i < k; i++)
		b[a[i][0]]++;                           //????????????????
	while(j < n)
	{
		if(b[j] == 0)                           //????????????
		{
			for(i = 0; i < k; i++)
				if(a[i][1] == j)
					count[j]++;                 //??????????????????
			if(count[j] == n - 1)
			{
				t++;
				cout << j << endl;              //????????????????????
			}
			j++;
		}
		else
			j++;
	}
	if(t == 0)
		cout << "NOT FOUND" << endl;            //?????????????NOT FOUND
	return 0;
}
