import sys
from collections import defaultdict

input = sys.stdin.buffer.readline


class UnionFind:
    def __init__(self, n):
        self.n = n
        self.parent = [i for i in range(n)]
        self.height = [1] * n
        self.size = [1] * n

    def find(self, x):
        if self.parent[x] == x:
            return x
        else:
            self.parent[x] = self.find(self.parent[x])
            return self.parent[x]

    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.height[x] < self.height[y]:
                self.parent[x] = y
                self.size[y] += self.size[x]
            else:
                self.parent[y] = x
                self.size[x] += self.size[y]
                if self.height[x] == self.height[y]:
                    self.height[x] += 1

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

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

    def group_members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parent) if i == x]

    def group_count(self):
        return len(self.roots())


N, M = map(int, input().split())
d = defaultdict(list)
for _ in range(N):
    b, c = map(int, input().split())
    b -= 1
    d[c].append(b)
d = dict(d)
uf = UnionFind(M)
for v in d.values():
    for i in range(len(v) - 1):
        uf.unite(v[i], v[i + 1])
print(M - uf.group_count())