n,m=map(int,input().split())
X=[None]
for i in range(n):
	X.append([0,0])
for i in range(m):
	a,b=map(int,input().split())
	X[a][0]+=1
	X[b][1]+=1
ans=0
for i in range(1,n+1):
	ans+=abs(X[i][0]-X[i][1])
print(ans//2-1)