#UnionFind
from collections import defaultdict

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 roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

n,m=map(int,input().split())
uf=UnionFind(m+1)
color=[[] for i in range(n+1)]
for _ in range(n):
  b,c=map(int,input().split())
  color[c].append(b)

for i in range(n+1):
  for j in color[i][1:]:
    uf.union(color[i][0],j)

ans=0
for i in uf.roots():
  ans+=-uf.parents[i]-1

print(ans)