import types

_atcoder_code = """
# Python port of AtCoder Library.

__version__ = '0.0.1'
"""

atcoder = types.ModuleType('atcoder')
exec(_atcoder_code, atcoder.__dict__)

_atcoder_dsu_code = """
import typing


class DSU:
    '''
    Implement (union by size) + (path halving)

    Reference:
    Zvi Galil and Giuseppe F. Italiano,
    Data structures and algorithms for disjoint set union problems
    '''

    def __init__(self, n: int = 0) -> None:
        self._n = n
        self.parent_or_size = [-1] * n

    def merge(self, a: int, b: int) -> int:
        assert 0 <= a < self._n
        assert 0 <= b < self._n

        x = self.leader(a)
        y = self.leader(b)

        if x == y:
            return x

        if -self.parent_or_size[x] < -self.parent_or_size[y]:
            x, y = y, x

        self.parent_or_size[x] += self.parent_or_size[y]
        self.parent_or_size[y] = x

        return x

    def same(self, a: int, b: int) -> bool:
        assert 0 <= a < self._n
        assert 0 <= b < self._n

        return self.leader(a) == self.leader(b)

    def leader(self, a: int) -> int:
        assert 0 <= a < self._n

        parent = self.parent_or_size[a]
        while parent >= 0:
            if self.parent_or_size[parent] < 0:
                return parent
            self.parent_or_size[a], a, parent = (
                self.parent_or_size[parent],
                self.parent_or_size[parent],
                self.parent_or_size[self.parent_or_size[parent]]
            )

        return a

    def size(self, a: int) -> int:
        assert 0 <= a < self._n

        return -self.parent_or_size[self.leader(a)]

    def groups(self) -> typing.List[typing.List[int]]:
        leader_buf = [self.leader(i) for i in range(self._n)]

        result: typing.List[typing.List[int]] = [[] for _ in range(self._n)]
        for i in range(self._n):
            result[leader_buf[i]].append(i)

        return list(filter(lambda r: r, result))
"""

atcoder.dsu = types.ModuleType('atcoder.dsu')
exec(_atcoder_dsu_code, atcoder.dsu.__dict__)
DSU = atcoder.dsu.DSU

# from atcoder.dsu import DSU
m = int(input())
n = 2 * 10 ** 5
deg = [0] * n
deg = [0] * n
to = [[] for _ in range(n)]
hw = [tuple(x - 1 for x in map(int, input().split())) for _ in range(m)]
for h, w in hw:
    to[h].append(w)
    deg[h] += 1
    deg[w] -= 1

d = DSU(n)
for i in range(n):
    for j in to[i]:
        d.merge(i, j)
x = hw[0][0]
s = set()
for h, w in hw: 
    if not (d.same(h, x) and d.same(w, x)):
        print(0)
        exit()
    s.add(h)
    s.add(w)

if not any(deg):
    print(len(s))
else:
    cnt0 = cnt1 = 0
    x = y = -1
    for i, d in enumerate(deg):
        if d == 0:
            continue
        elif d == 1:
            cnt0 += 1
        elif d == -1:
            cnt1 += 1
        else:
            cnt0 = 55
            break
    if cnt0 == cnt1 == 1:
        print(1)
    else:
        print(0)