import math
from bisect import bisect_left, bisect_right
from typing import Generic, Iterable, Iterator, TypeVar, Union, List

T = TypeVar("T")


# https://github.com/tatyam-prime/SortedSet/blob/main/SortedSet.py
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


from collections import defaultdict

v = SortedSet()
v.add((10**9 + 5 << 30) + 0)
ar = defaultdict(int)
n = int(input())
mask = (1 << 30) - 1
for i in range(n):
    l, r = map(int, input().split())
    r += 1
    tt = v.lt(l << 30)  # l 未満
    te = v.ge(l << 30)  # l 以上

    if tt == None:
        while te != None:
            teval = te >> 30
            teind = te & mask
            if teval == 10**9 + 5:
                v.discard(te)
                v.add((10**9 + 5 << 30) + r - l)
                break
            tr = te
            te = v.gt(te)
            tenind = te & mask
            if r - l < tenind:
                v.discard(tr)
                v.add((teval + r - l - teind << 30) + r - l)
                break
            v.discard(tr)
        v.add((l << 30) + 0)
        continue

    ttval = tt >> 30
    ttind = tt & mask
    teval = te >> 30
    teind = te & mask

    if ttval + teind - ttind <= l:
        gogo = teind
    else:
        gogo = ttind + l - ttval

    while te != None:
        teval = te >> 30
        teind = te & mask
        if teval == 10**9 + 5:
            v.discard(te)
            v.add((10**9 + 5 << 30) + gogo + r - l)
            break
        tr = te
        te = v.gt(te)
        tenind = te & mask
        if tenind > gogo + r - l:
            v.discard(tr)
            v.add((teval + gogo + r - l - teind << 30) + gogo + r - l)
            break
        v.discard(tr)
    v.add((l << 30) + gogo)

print(v.ge((10**9 + 2) << 30) & mask)
