PQR = list(map(int,input().split()))
sump = sum(PQR)
PQR += PQR

ans = 0
for i in range(3):
    p = PQR[i]/sump
    q = PQR[i+1]/sump
    r = PQR[i+2]/sump
    ans = max(ans,p,q+r)
print(ans)