class Union:
  def __init__(s, num):
    s.T = [-1] * num

  def root(s, x):
    if s.T[x] < 0: return x
    t = s.root(s.T[x])
    s.T[x] = t
    return t

  def merge(s, x, y):
    an, bn = s.root(x), s.root(y)
    if an == bn: return False
    am, bm = -s.T[an], -s.T[bn]
    if am < bm: an, bn = bn, an
    s.T[an] += s.T[bn]
    s.T[bn] = an
    return True

  def size(s, x):
    n = s.root(x)
    return -s.T[n]

  def same(s, x, y):
    return s.root(x) == s.root(y)

  def print(s): #デバッグ用
    print(*s.T)
    ans = []
    for i in range(len(s.T)):
      ans.append(s.root(i))
    print(*ans)

N, M = list(map(int, input().split()))
XY = [list(map(int, input().split())) for _ in range(N)]

cnt = 0
R = {}
for x, y in XY:
  if x not in R:
    R[x] = cnt
    cnt += 1
  if y not in R:
    R[y] = cnt
    cnt += 1

D = [0] * cnt
uni = Union(cnt)
ans = 0
for x, y in XY:
  x = R[x]
  y = R[y]
  v = max(D[uni.root(x)], D[uni.root(y)])
  u = min(D[uni.root(x)], D[uni.root(y)])
  if uni.merge(x, y):
    if u != 1:
      ans += 1
    D[uni.root(x)] = v
  else:
    t = uni.root(x)
    if D[t] == 0:
      D[t] = 1
      ans += 1

print(ans)