t = int(input())
x, a = map(int, input().split())
y, b = map(int, input().split())

if t > 0:
    left = 0
    right = t // y
else:
    t_ = abs(t)
    left = (t_ + b - 1) // b
    right = b // y + (t_ + b - 1) // b

ans = 10**18
for c in range(left, right + 1):
    q, r = divmod(t + c * b, a)
    ans = min(ans, r + q * x + c * y)
print(ans)