
int main(int argc, char* argv[])
{
	int i,j,mingren = 0;
	int count;
	int *person = NULL;
	int num = 0;
	int temp1,temp2;

	scanf("%d", &num);
	count = num;

	int **relation=(int **)malloc(num*sizeof(int *));
	for(i = 0; i < num; i ++)
	{
		relation[i]=(int *)malloc(num * sizeof(int));
	}
	//?????,?????????
	do 
	{
		scanf("%d %d", &temp1, &temp2);
		relation[temp1][temp2] = 1;
	} while (temp2 != 0 || temp1 != 0);
	//////////////////////////////////////////////////////////
	temp1 = 0;
	temp2 = 1;
	for (i = 0; i < num-2; i ++)
	{
		if(relation[temp1][temp2] == 1)
		{
			temp1 = num-1-i;
		}
		else
		{
			temp2 = num-1-i;
		}
	}
	if(relation[temp1][temp2] == 1)
	{
		mingren = temp2;
	}
	else
	{
		mingren = temp1;
	}
	
	for (i = 0; i < num; i ++)//?????????
	{
		if (i != mingren)
		{
			if(relation[i][mingren] == 0 || relation[mingren][i] == 1)
			{
				mingren = -1;
				break;
			}
		}
	}

	///////////////////////////////////////////////////////////

	if (mingren == -1)
	{
		printf("NOT FOUND\n");
	}
	else
	{
		printf("%d\n", mingren);
	}

	for(i = 0; i < num; i ++)
	{
		free(relation[i]);
	}
	free(relation);

	return 0;
}