import sys
from itertools import permutations
from heapq import heappop,heappush
from collections import deque
import random
import bisect

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

class SegmentTree:
    def __init__(self, init_val, segfunc, ide_ele):
        n = len(init_val)
        self.segfunc = segfunc
        self.ide_ele = ide_ele
        self.num = 1 << (n - 1).bit_length()
        self.tree = [ide_ele] * 2 * self.num
        self.size = n
        for i in range(n):
            self.tree[self.num + i] = init_val[i]
        for i in range(self.num - 1, 0, -1):
            self.tree[i] = self.segfunc(self.tree[2 * i], self.tree[2 * i + 1])

    def update(self, k, x):
        k += self.num
        self.tree[k] = x
        while k > 1:
            k >>= 1
            self.tree[k] = self.segfunc(self.tree[2*k], self.tree[2*k+1])

    def query(self, l, r):
        if r==self.size:
            r = self.num

        res = self.ide_ele

        l += self.num
        r += self.num
        right = []
        while l < r:
            if l & 1:
                res = self.segfunc(res, self.tree[l])
                l += 1
            if r & 1:
                right.append(self.tree[r-1])
            l >>= 1
            r >>= 1

        for e in right[::-1]:
            res = self.segfunc(res,e)
        return res

"""
結婚定理で考える
区間の和集合が区間になるような組のみ考えればいい
（区間の長さ）< (区間の数) である組があれば答えは0
そうでないなら条件を満たすkの範囲は区間になっているので、端点を考えればいい
"""
    
N = int(input())
lr = []
val_set = set()
for i in range(N):
    l,r = mi()
    val_set.add(l)
    val_set.add(r+1)
    lr.append((l,r+1))

val_set = sorted(val_set)
comp = {e:i for i,e in enumerate(val_set)}
lr = [(comp[l],comp[r]) for l,r in lr]
lr.sort(key=lambda x:x[0],reverse=True)
n = len(comp)

seg = SegmentTree([0]*n,max,0)
L,R = -10**9,10**9
for l,r in lr:
    t = seg.query(l,r) + 1
    ll = val_set[l]
    L = max(L,t-N+ll-1)
    seg.update(l,t)

seg = SegmentTree([0]*n,max,0)
lr.sort(key=lambda x:x[1],reverse=False)
for l,r in lr:
    t = seg.query(l,r) + 1
    rr = val_set[r] - 1
    R = min(R,rr-t)
    seg.update(r-1,t)

m = min(val_set)
for i,(l,r) in enumerate(lr):
    if val_set[r]-m < i+1:
        print(0)
        break
else:
    #assert False
    print(R-L+1)