import sys

input = sys.stdin.readline

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

t = float(n - d)

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

else: print(((m - 1) * 2 * t / pow(n, 2)))
import sys

input = sys.stdin.readline

N, M, D = list(map(float, input().split()))

print(((M - 1) / N + ((N - 2 * D) > 0 and (D > 0)) * (N - 2 * D) * (M - 1) / (N ** 2)))
import sys

input = sys.stdin.readline
n, m, d = list(map(float, input().split()))
t = float(n - d)
if d == 0:
    print(((m - 1) * (1 / n)))
else:
    print(((m - 1) * 2 * t / pow(n, 2)))

import sys

input = sys.stdin.readline
N, M, D = list(map(float, input().split()))
print(((M - 1) / N + ((N - 2 * D) > 0 and (D > 0)) * (N - 2 * D) * (M - 1) / (N**2)))

-n, m, d = list(map(float, input().split())) -t = float(n - d) -if d == 0: -    print(((m - 1) * (1 / n))) -else: -    print(((m - 1) * 2 * t / pow(n, 2))) +N, M, D = list(map(float, input().split())) +print(((M - 1) / N + ((N - 2 * D) > 0 and (D > 0)) * (N - 2 * D) * (M - 1) / (N**2)))