import sys
import math
from collections import deque,Counter
#sys.setrecursionlimit(10**7)
int1=lambda x: int(x)-1

inp=lambda :int(input())
mi=lambda :map(int,input().split())
li=lambda :list(mi())
mi1=lambda :map(int1,input().split())
li1=lambda :list(mi1())
mis=lambda :map(str,input().split())
lis=lambda :list(mis())
pr=print

from collections import defaultdict
"""
#初期値 0
d=defaultdict(int)

#初期値 1
d=defaultdict(lambda:1)
"""

mod=10**9+7
Mod=998244353
INF=10**18
ans=0

n=inp()
h=[0]*200001
w=[0]*200001
for i in range(n):
  a,b=mi()
  h[a]+=1
  w[b]+=1
x=0
for i in range(200001):
  if h[i]!=w[i]:
    x+=1
if x==2:
  print(1)
elif x==0:
  print(n)
else:
  print(0)