N,M=map(int,input().split())
box=[set() for _ in range(N)] #色ごとに箱を格納
for _ in range(M):
  b,c=map(int,input().split())
  box[c-1].add(b)
ans=0
for i in range(N):
  ans+=max(0,len(box[i])-1)
print(ans)