A = input()
B = A.split()
n = int(B[0])
k = int(B[1])
if 1 <= n and n <= 6 and 1 <= k and k <= 1000:
    d = (50 * n) / (0.8 + 0.2 * k)
    e = int(d)
    S = 50 * n + e
    print(S)