import sys
sys.setrecursionlimit(10 ** 6)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LC(): return list(input())
def IC(): return [int(c) for c in input()]
def MI(): return map(int, sys.stdin.readline().split())
INF = float('inf')
MOD = 10**9 + 7
def solve():
    A,B,C = MI()
    s = (A+B+C)/2
    import math
    S = math.sqrt(s*(s-A)*(s-B)*(s-C))
    Tmp = (C*(A/2)*2*S*(B/2) + B*(C/2)*2*S*(A/2) + A*(B/2)*2*S*(C/2))/(2*A*B*C)
    print(S-Tmp)
    return
solve()