#!/usr/bin/env python3
import re

lines = (x.strip() for x in open("input.txt"))
target = 2000000
intervals = []
known_targets = set()

for line in lines:
    x, y, a, b = map(int, re.search(r"(-?\d+).+?(-?\d+).+?(-?\d+).+?(-?\d+)", line).groups())
    dist = abs(x-a) + abs(y-b)
    width = dist-abs(y-target)
    if width >= 0:
        intervals.append((x-width, x+width))
    if b == target:
        known_targets.add(a)
    if y == target:
        known_targets.add(x)


intervals.sort(key=lambda x: x[0])
merged = [intervals[0]]
for i in intervals[1:]:
    if merged[-1][1] >= i[0]:
        merged[-1] = (merged[-1][0], max(merged[-1][1], i[1]))
    else:
        merged.append(i)

print(sum(b-a+1 for a, b in merged)-len(known_targets))