T = int(input())
X, A = map(int, input().split())
Y, B = map(int, input().split())
ans = 10 ** 18

if T > 0:
    for r in range(T//Y + 1):
        q, p = divmod(T + B * r, A)
        ans = min(ans, p + X * q + Y * r)
else:
    T = -T
    minv = (T + B - 1)//B
    maxv = B * minv - T + minv
    for r in range(minv, maxv + 1):
        q, p = divmod(r * B - T, A)
        ans = min(ans, p + X * q + Y * r)
print(ans)