import sys, re, itertools
# ranges are inclusive from both ends

def range_intersect(a, b):
	return a[0] <= b[0] <= a[1] or a[0] <= b[1] <= a[1] or b[0] <= a[0] <= b[1] or b[0] <= a[1] <= b[1]

class RangeSet:
	def __init__(self):
		self.rs = []
	def add(self, a, b):
		for i in range(len(self.rs)):
			r = self.rs[i]
			if range_intersect(r, (a, b)):
				a = min(a, r[0])
				b = max(b, r[1])
				self.rs[i] = None
		self.rs = [r for r in self.rs if r]
		self.rs.append((a, b))
	def size(self):
		s = 0
		for r in self.rs:
			s += r[1] - r[0] + 1
		return s

data = []
for line in sys.stdin:
	data.append([int(n) for n in re.findall('-?\d+', line)])

def manhattan(a):
	return abs(a[0] - a[2]) + abs(a[1] - a[3])

def partOne(y):
	r = RangeSet()
	for l in data:
		m = manhattan(l)
		w = m - abs(l[1] - y)
		if w < 0: continue
		r.add(l[0] - w, l[0] + w)
	beacons = set([(a[2], a[3]) for a in data if a[3] == y])
	return r.size() - len(beacons)

def vis(size):
	s = ''
	for y in range(size):
		for x in range(size):
			c = ' '
			for l in data:
				m = abs(l[0] - l[2]) + abs(l[1] - l[3])
				if abs(l[0] - x) + abs(l[1] - y) <= m:
					c = '#'
					break
			if (x, y) in [(a[0], a[1]) for a in data]:
				c = 'S'
			if (x, y) in [(a[2], a[3]) for a in data]:
				c = 'B'
			s += c
		s += '\n'
	return s

def partTwo():
	for y in range(4000000):
		if y % 4000 == 0: print(y / 40000)
		r = RangeSet()
		for l in data:
			m = manhattan(l)
			w = m - abs(l[1] - y)
			if w < 0: continue
			r.add(l[0] - w, l[0] + w)
		l = len(r.rs)
		if l == 0: break
		if l != 1:
			print(r.rs, y)
			x = r.rs[0][1] + 1
			return 4000000 * x + y

#print(partOne(2000000))
print(partTwo())