from math import sqrt,sin,cos,tan,ceil,radians,floor,gcd,exp,log,log10,log2,factorial,fsum
from heapq import heapify, heappop, heappush
from bisect import bisect_left, bisect_right
from copy import deepcopy
import copy
import random
from collections import deque,Counter,defaultdict
from itertools import permutations,combinations
from decimal import Decimal,ROUND_HALF_UP
#tmp = Decimal(mid).quantize(Decimal('0'), rounding=ROUND_HALF_UP)
from functools import lru_cache, reduce
#@lru_cache(maxsize=None)
from operator import add,sub,mul,xor,and_,or_,itemgetter
INF = 10**18
mod1 = 10**9+7
mod2 = 998244353

#DecimalならPython
#再帰ならPython!!!!!!!!!!!!!!!!!!!!!!!!!!

def scc(N,edges):
    M=len(edges)
    start=[0]*(N+1)
    elist=[0]*M
    for e in edges:
        start[e[0]+1]+=1
    for i in range(1,N+1):
        start[i]+=start[i-1]
    counter=start[:]
    for e in edges:
        elist[counter[e[0]]]=e[1]
        counter[e[0]]+=1
    visited=[]
    low=[0]*N
    Ord=[-1]*N
    ids=[0]*N
    NG=[0,0]
    def dfs(v):
        stack=[(v,-1,0),(v,-1,1)]
        while stack:
            v,bef,t=stack.pop()
            if t:
                if bef!=-1 and Ord[v]!=-1:
                    low[bef]=min(low[bef],Ord[v])
                    stack.pop()
                    continue
                low[v]=NG[0]
                Ord[v]=NG[0]
                NG[0]+=1
                visited.append(v)
                for i in range(start[v],start[v+1]):
                    to=elist[i]
                    if Ord[to]==-1:
                        stack.append((to,v,0))
                        stack.append((to,v,1))
                    else:
                        low[v]=min(low[v],Ord[to])
            else:
                if low[v]==Ord[v]:
                    while(True):
                        u=visited.pop()
                        Ord[u]=N
                        ids[u]=NG[1]
                        if u==v:
                            break
                    NG[1]+=1
                low[bef]=min(low[bef],low[v])
    for i in range(N):
        if Ord[i]==-1:
            dfs(i)
    for i in range(N):
        ids[i]=NG[1]-1-ids[i]
    group_num=NG[1]
    counts=[0]*group_num
    for x in ids:
        counts[x]+=1
    groups=[[] for i in range(group_num)]
    for i in range(N):
        groups[ids[i]].append(i)
    return groups
# edge = [(a,b)]

'''
グラフっぽく考えられそう
最初と終わりさえ決めれば間は関係ない
全部を通って終わりまでたどりつけるか？という問題

sccして1個なら全部行ける
1個じゃなくて、パスがあったらその組はいける

入次数0から始める
そこから全部通れるか
サイクルはSCCで対処可能
'''

M = int(input())
lim = 2*(10**5)+1
G = [[] for _ in range(M+1)]
lef = [[] for _ in range(lim)]
rig = [[] for _ in range(lim)]

hw = []
st = set()
for i in range(1,M+1):
    h,w = map(int, input().split())
    if (h,w) in st:
        continue
    st.add((h,w))
    lef[h].append(i)
    rig[w].append(i)
    hw.append((h,w))

N = len(hw)
memo = [0]*(N+1)
edge = []
for i in range(1,N+1):
    h,w = hw[i-1]
    for j in lef[w]:
        G[i].append(j)
        edge.append((i,j))
        memo[j] += 1
    for j in rig[h]:
        G[j].append(i)
        edge.append((j,i))
        memo[i] += 1

SCC = scc(N+1,edge)

if len(SCC) == 2:
    print(N)
else:
    Q = []
    seen = [0]*(N+1)
    for i in range(1,N+1):
        if memo[i] == 0:
            Q.append(i)
            break
    
    while len(Q) > 0:
        pos = Q.pop()
        seen[pos] = 1
        
        for nx in G[pos]:
            if seen[nx] == 1:
                continue
            Q.append(nx)
            break
    
    for i in range(1,N+1):
        if seen[i] == 0:
            print(0)
            break
    else:
        print(1)