C,D=map(int,input().split())

MIN=0
MAX=min(C*4/3,D*4)

def calc(x):
    C2=C-x*3/4
    D2=D-x/4

    y=min(C2*7/2,D2*7/5)

    return x*1000+y*2000

for i in range(1000):
    #print(MIN,MAX)

    mid1=MIN+(MAX-MIN)/3
    mid2=MIN+(MAX-MIN)/3*2

    if calc(mid1)>calc(mid2):
        MAX=mid2
    else:
        MIN=mid1

print(calc((MAX+MIN)/2))