N=int(input())
l=0
r=10**10
L=[]
R=[]
h=[]
u=10**10
for i in range(N):
  a,b=map(int,input().split())
  L.append(a-1)
  R.append(b-1)
  h.append([a-1,b-1])
  u=min(u,a-1)
L.sort()
R.sort()
for i in range(N):
  l=max(l,L[i]-i)
for i in range(N):
  r=min(r,R[i]-i)
if l>r:
  print(0)
  exit()
ans=r-l+1
if ans>10**2:
  print(ans)
  exit()
p=0
for i in range(N):
  h[i][0]-=u
  h[i][1]-=u
  p=max(p,h[i][0])
if p>10**7:
  print(ans)
  exit()
G=[[] for i in range(p+1)]
for i in range(N):
  x,y=h[i][:]
  G[x].append(y)
result=0
from heapq import heappush,heappop
for k in range(l-u,r-u+1):
  S=[]
  b=True
  for x in range(k):
    for y in G[x]:
      heappush(S,y)
  for i in range(N):
    t=i+k
    if t<=p:
      for y in G[t]:
        heappush(S,y)
    if len(S)==0:
      b=False
      break
    w=heappop(S)
    if w<t:
      b=False
      break
  if b==True:
    result+=1
print(result)