import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**16
md = 998244353
# md = 10**9+7

class UnionFind:
    def __init__(self, n):
        self.state = [-1]*n
        self.size_table = [1]*n
        # cntはグループ数
        self.cnt = n

    def root(self, u):
        stack = []
        while self.state[u] >= 0:
            stack.append(u)
            u = self.state[u]
        for v in stack: self.state[v] = u
        return u

    def merge(self, u, v):
        u = self.root(u)
        v = self.root(v)
        if u == v: return
        du = -self.state[u]
        dv = -self.state[v]
        if du < dv: u, v = v, u
        if du == dv: self.state[u] -= 1
        self.state[v] = u
        self.cnt -= 1
        self.size_table[u] += self.size_table[v]
        return

    # グループの要素数
    def size(self, u):
        return self.size_table[self.root(u)]

mx=200005
# mx = 20
n = II()
uf = UnionFind(mx)
deg = [0]*mx
st = set()
u = -1
for i in range(n):
    h, w = LI()
    deg[h] -= 1
    deg[w] += 1
    uf.merge(h, w)
    st.add(h)
    st.add(w)
    u = h

def findsg():
    if uf.size(u) != len(st):
        return -2, -2
    s = g = -1
    for v in range(mx):
        if abs(deg[v]) > 1: return -2, -2
        if deg[v] == 1:
            if s == -1:
                s = v
            else:
                return -2, -2
        if deg[v] == -1:
            if g == -1:
                g = v
            else:
                return -2, -2
    return s, g

s, g = findsg()
if s == -2:
    print(0)
elif s == -1:
    print(len(st))
else:
    print(1)