int map[9000][9000];
int main()
{
	int n, i, j;
	int found = 0;
	scanf("%d%d%d", &n,&i,&j);
	while ((i != 0)||(j != 0))
	{
		map[i][j] = 1;
		scanf("%d%d", &i, &j);
	}
	for (i = 0; i < n; i++)
	{
		int mark = 0;
		for (j = 0; j < n; j++)
		{
			if ((map[i][j] == 1)&&(i != j))
			{
				mark = 1;
				break;
			}
		}
		if (mark == 0)
		{
			int mark2 = 0;
			for (j = 0; j < n; j++)
			{
				if ((j != i)&&(map[j][i] == 1))
					mark2++;
			}
			if (mark2 == n-1)
			{
				found = 1;
				printf("%d\n", i);
				break;
			}
		}
	}
	if (found == 0)
		printf("NOT FOUND\n");
	return 0;
}


