A1

c, x, y, z, m, s, f, e, t = map(int, input().split())
i=0
count=0
while i<c:
    if c>x:
        count=count+m
        i=i+s-y
        x=x+z
    else:
        i=i+s
        if i>x:
            i=x
        count=count+m
p=0
cp=0
coin=0
cl=0
while p<=e:
    if f>coin:
        cp=cp+m
        coin=coin+s
    else:
        cl=coin/f
        p=p+int(cl)
        if p>e:
            cp=cp+t
if count>cp:
    print(cp)
if cp>count:
    print(count)