t = int(input())
x,a = map(int,input().split())
y,b = map(int,input().split())
ans = 10 ** 15

cnt = 0
while cnt  <= t:
    p_ans = ans
    if cnt * a <= t:
        ans = min(ans,x*cnt + t-a * cnt)
    else:
        ans = min(ans,x*cnt + (-((-(a*cnt-t))//b)) * y +  t - (a*cnt - (-((-(a*cnt-t))//b)) * b))
    cnt += 1

cnt = 0 
b *= -1
while -cnt  >=  t:
    if cnt * b <= t:
        p_ans = ans
        ans = min(ans,y * cnt +  ((t - b*cnt)//a) * x + t - (cnt * b  + ((t - b*cnt)//a) * a))
    cnt += 1
print(ans)