class UnionFind:
    def __init__(self, n):
        self.par = [i for i in range(n+1)]
        self.rank = [0] * (n + 1)
        self.size = [1] * (n + 1)
 
    # 検索
    def find(self, x):
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]
 
    # 併合
    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.rank[x] < self.rank[y]:
            self.par[x] = y
            self.size[y] += self.size[x]
        else:
            self.par[y] = x
            self.size[x] += self.size[y]
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1
 
    # 同じ集合に属するか判定
    def same_check(self, x, y):
        return self.find(x) == self.find(y)

n, m = map(int, input().split())
a = [[] for _ in range(n)]
uf = UnionFind(m)
for i in range(n):
    b, c = map(int, input().split())
    a[c - 1].append(b - 1)
for i in range(n):
    for j in range(len(a[i]) - 1):
        uf.unite(a[i][j], a[i][j + 1])
d = [0] * m
ans = 0
for i in range(m):
    i = uf.find(i)
    if d[i]:
        continue
    ans += uf.size[i] - 1
    d[i] = 1
print(ans)