from collections import defaultdict


class UnionFind:
    def __init__(self, n: int):
        self.data = [-1] * (n+1)
        self.nexts = [i for i in range(n+1)]

    def root(self, a: int) -> int:
        if self.data[a] < 0: return a
        self.data[a] = self.root(self.data[a])
        return self.data[a]

    def unite(self, a: int, b: int) -> bool:
        pa = self.root(a)
        pb = self.root(b)
        if pa == pb: return False
        if self.data[pa] > self.data[pb]:
            pa, pb = pb, pa
        self.data[pa] += self.data[pb] # pa を pb をつなげる
        self.data[pb] = pa
        self.nexts[pa], self.nexts[pb] = self.nexts[pb], self.nexts[pa]
        return True

    def issame(self, a: int, b: int) -> bool:
        return self.root(a) == self.root(b)

    def size(self, a: int) -> int:
        """a が属する集合のサイズ"""
        return -self.data[self.root(a)]

    def group(self, a: int):
        """a が属する集合"""
        yield a
        x = a
        while self.nexts[x] != a:
            x = self.nexts[x]
            yield x


N, M = map(int, input().split())
freq = defaultdict(set)
for _ in range(N):
    b, c = map(int, input().split())
    b -= 1
    freq[c].add(b)

uf = UnionFind(M)
for bs in map(list, freq.values()):
    hd = bs[0]
    for i in range(len(bs)):
        uf.unite(hd, bs[i])

ans = 0
used = set()
for i in range(M):
    r = uf.root(i)
    if r in used: continue
    used.add(r)
    ans += uf.size(r) - 1

print(ans)