import decimal

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

print((decimal.Decimal(((2**min(1,d))*(n-d)*(m-1))/(n**2))))

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

print((((2**min(1,d))*(n-d)*(m-1))/(n**2)))

import decimal

n, m, d = list(map(int, input().split()))
print((decimal.Decimal(((2 ** min(1, d)) * (n - d) * (m - 1)) / (n**2))))

n, m, d = list(map(int, input().split()))
print((((2 ** min(1, d)) * (n - d) * (m - 1)) / (n**2)))

-import decimal - -print((decimal.Decimal(((2 ** min(1, d)) * (n - d) * (m - 1)) / (n**2)))) +print((((2 ** min(1, d)) * (n - d) * (m - 1)) / (n**2)))