#int(input())
#map(int, input().split())
#list(map(int, input().split()))

T = int(input())
X, A = map(int, input().split())
Y, B = map(int, input().split())

m = 10 ** 7 + 1
if T > 0:
    ans = T
    for i in range(m):
        a, b = divmod(T + i*B, A)
        ans = min(i*Y + a*X + b, ans)
        if ans < i*Y:
            break
else:
    a, b = divmod(T, B)
    t = -a * Y
    T += B * -a
    # print(a, b, t, T)
    ans = T
    for i in range(m):
        a, b = divmod(T + i*B, A)
        ans = min(i*Y + a*X + b, ans)
        if ans < i*Y:
            break
    ans += t

print(ans)