import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 61 - 1
mod = 998244353
import heapq
n = ii()

LR = []
lr = []
for i in range(n):
    l, r = mi()
    lr.append((l, r))
    LR.append((l, -1))
    LR.append((r, 1))
LR.sort()

LR2 = [[0, 0] for _ in range(n)]
lcnt = 0
rcnt = 0
for v, x in LR:
    if x == -1:
        LR2[lcnt][0] = v
        lcnt += 1
    else:
        LR2[rcnt][1] = v
        rcnt += 1
    
mink = -inf
maxk = inf
LR2 = LR2[::]
for i in range(n):
    l, r = LR2[i]
    mink = max(mink, l - i)
    maxk = min(maxk, r - i)
ans = max(0, maxk - mink + 1)
now = mink
cnt = 0
q = []
nex = []
for l, r in lr:
    if l < now <= r:
        heapq.heappush(q, r)
    elif r >= now:
        nex.append((l, r))
    else:
        ans = 0
        break
        
nex.sort()


for l, r in nex:
    if l > now:
        ans = 0
        break
    heapq.heappush(q, r)
    to = heapq.heappop(q)
    if to < now:
        ans = 0
        break
    now += 1
    
print(ans)