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
    
def checK_zero(N,_lr):
    lr = _lr[:]
    lr.sort(key=lambda x:x[0],reverse=True)
    nxt_num = 0
    pq = []
    while lr or pq:
        while lr and lr[-1][0] <= nxt_num:
            l,r = lr.pop()
            heappush(pq,r)
        #print(lr,pq,nxt_num)
        if pq:
            r = heappop(pq)
            if r < nxt_num:
                #print("ban!",pq,lr,nxt_num)
                return False
            nxt_num += 1
        else:
            l,r = lr[-1]
            nxt_num = l
    return True

def check_k(N,k,_lr):
    lr = [(l-k,r-k) for l,r in _lr]
    lr.sort(key=lambda x:x[0],reverse=True)

    pq = []
    for i in range(1,N+1):
        while lr and lr[-1][0] <= i:
            heappush(pq,lr.pop()[1])
        if not pq:
            return False
        r = heappop(pq)
        if r < i:
            return False
    return True

def solve_brute(N,lr):
    res = []
    R = max(r for l,r in lr)
    for k in range(-N,R+1):
        if check_k(N,k,lr):
            res.append(k)
    return res

def solve(N,_lr):
    if not checK_zero(N,_lr):
        return 0
        return []
    
    lr = [(l,r+1) for l,r in _lr]

    


        

    """
    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 = 相異なる整数を割り当てられるか？
    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
    """

    
    
    val_set = set()
    for i,(l,r) in enumerate(lr):
        val_set.add(l)
        val_set.add(r)
        


    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)

    cnt = [0] * (n)
    for l,r in lr:
        cnt[l] += 1
        cnt[r] -= 1
    for i in range(1,n):
        cnt[i] += cnt[i-1]
    if 0 in cnt[:n-1]:
        return 0
        return []

    L,R = -10**9,10**9
    for i,(l,r) in enumerate(lr):
        t = i + 1
        ll = val_set[l]
        L = max(L,t-N+ll-1)
        

    
    lr.sort(key=lambda x:(x[1],x[0]),reverse=False)
    for i,(l,r) in enumerate(lr):
        t = i + 1
        rr = val_set[r] - 1
        R = min(R,rr-t)
        

    #print("LR",L,R)
    if L <= R:
        return R-L+1
        return [k for k in range(L,R+1)]
    else:
        return 0
        return []

def make_test(N):
    lr = []
    for i in range(N):
        l = random.randint(1,2*N)
        r = random.randint(l,2*N)
        lr.append((l,r))
    return lr

while False:
    N = random.randint(1,10)
    lr = make_test(N)

    #N = 2
    #lr = [(1,4),(4,4)]

    #N = 3
    #lr = [(5,6),(6,6),(5,5)]

    #N = 4
    #lr = [(1,5),(5,7),(3,7),(7,7)]

    #N = 4
    #lr = [(2,7),(2,4),(4,6),(3,3)]

    res = solve(N,lr)
    exp = solve_brute(N,lr)
    if res != exp:
        print("WA")
        print(N)
        print(lr)
        print("res",res)
        print("exp",exp)
        break
    else:
        print("AC",N)

N = int(input())
lr = [tuple(mi()) for i in range(N)]
print(solve(N,lr))