import sys

INF = 1 << 60

MOD = 10**9 + 7 # 998244353

sys.setrecursionlimit(2147483647)

input = lambda:sys.stdin.readline().rstrip()

def resolve():

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

    ans = (m - 1) / n

    if d > 0 and 2 * d + 1 <= n:

        ans *= 1 + (n - 2 * d) / n

    print(ans) 

resolve()
import sys

INF = 1 << 60

MOD = 10**9 + 7 # 998244353

sys.setrecursionlimit(2147483647)

input = lambda:sys.stdin.readline().rstrip()

def resolve():

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

    if d == 0:

        print(((m - 1) / n))

    else:

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

resolve()
import sys

INF = 1 << 60
MOD = 10**9 + 7  # 998244353
sys.setrecursionlimit(2147483647)
input = lambda: sys.stdin.readline().rstrip()


def resolve():
    n, m, d = list(map(int, input().split()))
    ans = (m - 1) / n
    if d > 0 and 2 * d + 1 <= n:
        ans *= 1 + (n - 2 * d) / n
    print(ans)


resolve()

import sys

INF = 1 << 60
MOD = 10**9 + 7  # 998244353
sys.setrecursionlimit(2147483647)
input = lambda: sys.stdin.readline().rstrip()


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


resolve()

-    ans = (m - 1) / n -    if d > 0 and 2 * d + 1 <= n: -        ans *= 1 + (n - 2 * d) / n -    print(ans) +    if d == 0: +        print(((m - 1) / n)) +    else: +        print((2 * (m - 1) * (n - d) / (n * n)))