N=int(input())
A=[];c=10**10
for i in range(N):
  l,r=map(int, input().split())
  A.append((l,r))
  
A=sorted(A,key=lambda x: x[1])
A=sorted(A,key=lambda x: x[0])
#print(A)
B=[]
ll=-10**20;rr=10**20
for i in range(N):
  l,r=A[i]
  ll=max(ll,l-i)
  rr=min(rr,r-i)
p,q=ll,rr
#print(ll,rr)
  
A=sorted(A,key=lambda x: x[0])
A=sorted(A,key=lambda x: x[1])
#print(A)
ll=-10**20;rr=10**20
for i in range(N):
  l,r=A[i]
  ll=max(ll,l-i)
  rr=min(rr,r-i)
r,s=ll,rr
#print(p,q,r,s)
A=[]
if p<=q:
  A.append(p)
  A.append(q)
if r<=s:
  A.append(r)
  A.append(s)
ans=0
if len(A)>0:
  ans=max(A)-min(A)+1

print(ans)