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

n = ii()

LR = []

for i in range(n):
    l, r = mi()
    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
LR = LR2[::]
for i in range(n):
    l, r = LR[i]
    mink = max(mink, l - i)
    maxk = min(maxk, r - i)
print(max(0, maxk - mink + 1))