import sys # sys.setrecursionlimit(200005) int1 = lambda x: int(x)-1 pDB = lambda *x: print(*x, end="\n", file=sys.stderr) p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr) def II(): return int(sys.stdin.readline()) def LI(): return list(map(int, sys.stdin.readline().split())) def LLI(rows_number): return [LI() for _ in range(rows_number)] def LI1(): return list(map(int1, sys.stdin.readline().split())) def LLI1(rows_number): return [LI1() for _ in range(rows_number)] def SI(): return sys.stdin.readline().rstrip() dij = [(0, 1), (-1, 0), (0, -1), (1, 0)] # dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)] # inf = (1 << 63)-1 inf = (1 << 31)-1 md = 10**9+7 # md = 998244353 # Thanks for tatyam # https://github.com/tatyam-prime/SortedSet/blob/main/SortedSet.py import math from bisect import bisect_left, bisect_right from typing import Generic, Iterable, Iterator, TypeVar, Union, List T = TypeVar('T') class SortedSet(Generic[T]): BUCKET_RATIO = 50 REBUILD_RATIO = 170 def _build(self, a=None) -> None: "Evenly divide `a` into buckets." if a is None: a = list(self) size = self.size = len(a) bucket_size = int(math.ceil(math.sqrt(size/self.BUCKET_RATIO))) self.a = [a[size*i//bucket_size: size*(i+1)//bucket_size] for i in range(bucket_size)] def __init__(self, a: Iterable[T] = []) -> None: "Make a new SortedSet from iterable. / O(N) if sorted and unique / O(N log N)" a = list(a) if not all(a[i] < a[i+1] for i in range(len(a)-1)): a = sorted(set(a)) self._build(a) def __iter__(self) -> Iterator[T]: for i in self.a: for j in i: yield j def __reversed__(self) -> Iterator[T]: for i in reversed(self.a): for j in reversed(i): yield j def __len__(self) -> int: return self.size def __repr__(self) -> str: return "SortedSet"+str(self.a) def __str__(self) -> str: s = str(list(self)) return "{"+s[1: len(s)-1]+"}" def _find_bucket(self, x: T) -> List[T]: "Find the bucket which should contain x. self must not be empty." for a in self.a: if x <= a[-1]: return a return a def __contains__(self, x: T) -> bool: if self.size == 0: return False a = self._find_bucket(x) i = bisect_left(a, x) return i != len(a) and a[i] == x def add(self, x: T) -> bool: "Add an element and return True if added. / O(√N)" if self.size == 0: self.a = [[x]] self.size = 1 return True a = self._find_bucket(x) i = bisect_left(a, x) if i != len(a) and a[i] == x: return False a.insert(i, x) self.size += 1 if len(a) > len(self.a)*self.REBUILD_RATIO: self._build() return True def discard(self, x: T) -> bool: "Remove an element and return True if removed. / O(√N)" if self.size == 0: return False a = self._find_bucket(x) i = bisect_left(a, x) if i == len(a) or a[i] != x: return False a.pop(i) self.size -= 1 if len(a) == 0: self._build() return True def lt(self, x: T) -> Union[T, None]: "Find the largest element < x, or None if it doesn't exist." for a in reversed(self.a): if a[0] < x: return a[bisect_left(a, x)-1] def le(self, x: T) -> Union[T, None]: "Find the largest element <= x, or None if it doesn't exist." for a in reversed(self.a): if a[0] <= x: return a[bisect_right(a, x)-1] def gt(self, x: T) -> Union[T, None]: "Find the smallest element > x, or None if it doesn't exist." for a in self.a: if a[-1] > x: return a[bisect_right(a, x)] def ge(self, x: T) -> Union[T, None]: "Find the smallest element >= x, or None if it doesn't exist." for a in self.a: if a[-1] >= x: return a[bisect_left(a, x)] def __getitem__(self, x: int) -> T: "Return the x-th element, or IndexError if it doesn't exist." if x < 0: x += self.size if x < 0: raise IndexError for a in self.a: if x < len(a): return a[x] x -= len(a) raise IndexError def index(self, x: T) -> int: "Count the number of elements < x." ans = 0 for a in self.a: if a[-1] >= x: return ans+bisect_left(a, x) ans += len(a) return ans def index_right(self, x: T) -> int: "Count the number of elements <= x." ans = 0 for a in self.a: if a[-1] > x: return ans+bisect_right(a, x) ans += len(a) return ans # xy = [(12, 11), (18, 8), (27, 5), (6, 15)] # # ss = SortedSet(xy) # ss.add((0, inf)) # print(ss) # # a = (18, 13) # i = ss.index_right(a) # r = a[0] # b = ss[i][1] # ans = 0 # while 1: # x, y = ss[i-1] # ans += (a[1]-b)*(r-x) # if y > a[1]: break # ss.discard((x, y)) # r = x # b = y # i -= 1 # ss.add(a) # print(ans, ss) def push(z, x, y): a = (x, y) i = ss[z].index_right(a) if i < len(ss[z]) and ss[z][i][1] >= a[1]: return 0 res = 0 r = a[0] b = 0 if i == len(ss[z]) else ss[z][i][1] while 1: x, y = ss[z][i-1] res += (r-x)*(a[1]-b) if y > a[1]: break ss[z].discard((x, y)) r, b = x, y i -= 1 ss[z].add(a) return res n = II() ss = [SortedSet([(0, inf)]) for _ in range(4)] for _ in range(n): x1, y1, x2, y2 = LI() ans = 0 ans += push(0, x2, y2) ans += push(1, -x1, y2) ans += push(2, -x1, -y1) ans += push(3, x2, -y1) print(ans)