class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

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

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

def main():
    n = int(input())
    uf = UnionFind(2*10**5+1)
    loop = False
    s = set()
    for i in range(n):
        h, w = map(int, input().split())
        s.add(h)
        s.add(w)
        if h != w:
            if uf.same(h, w):
                loop = True
            uf.union(h, w)

    s = list(s)
    pr = uf.find(s[0])
    for i in s:
        if pr != uf.find(i):
            return 0
    if loop:
        return n
    else:
        return 1

print(main())