n = list(map(int, input().split()))

xy = [map(int, input().split()) for _ in range(n[0])]
x, y = [list(i) for i in zip(*xy)]

l = []

for i in range(1,n[0]+1):
  m = y.count(i)
  if m != 0:
    L = []
    for j in range(m):
      d = y.index(i)
      X = x.pop(d)
      Y = y.pop(d)
      L.append(X)
      LL = set(L)
    ANS = len(LL)-1
    l.append(ANS)
  else:
    pass
  
ans = sum(l)

print(ans)