from decimal import Decimal, ROUND_HALF_UP

N,K = map(int,input().split())

number = (N+1)*K


sum = 0
for i in range(N+1):
  for j in range(K):
    sum += float(i/number)

a = Decimal(str(sum))

b = a.quantize(Decimal('0.1'), rounding=ROUND_HALF_UP)

print(b)