# -*- coding: utf-8 -*-

n,m,d = map(float,input().split())

if d == 0:
    print((m-1)/n)
else:
    print(2*(n-d)*(m-1)/(n**2))

7de55fad447cfad76db7cec87e9af66840cf6fed
<mask token>

<mask token>
if d == 0:
    print((m - 1) / n)
else:
    print(2 * (n - d) * (m - 1) / n ** 2)

n, m, d = map(float, input().split())
if d == 0:
    print((m - 1) / n)
else:
    print(2 * (n - d) * (m - 1) / n ** 2)

# -*- coding: utf-8 -*-

n,m,d = map(float,input().split())

if d == 0:
    print((m-1)/n)
else:
    print(2*(n-d)*(m-1)/(n**2))
