def division(a,b):
    cnt = 0
    if type(a) == int:
        while a > b-1:
            a -= b
            cnt += 1
        return cnt
  
def f(a,b):
    return 50*a + division(50*a, 0.8 + 0.2*b)
  
A,B = map(int,input().split())
print(f(A,B))