p, q, r = map(int, input().split())
prob = [p/(p+q+r), q/(p+q+r), r/(p+q+r)]
pb = p/(p+q+r)
qb = q/(p+q+r)
rb = r/(p+q+r)

ans = 0
for signbox in range(3):
    stay = 0
    change = 0
    for diamondbox in range(3):
        if signbox != diamondbox:
            stay += prob[diamondbox]*0.5
            change += prob[diamondbox]*0.5
        else:
            stay += prob[diamondbox]
            change += 0
    ans = max(ans, stay, change)

print(ans)