t = int(input())
x,a = map(int,input().split())
y,b = map(int,input().split())
ans = 10 ** 15
if t >= 0:
    cnt = 0
    while cnt * a <= 2*10**7:
        if cnt * a <= t:
            ans = min(ans,x*cnt + t-a * cnt)
        else:
#             print(a*cnt,-((-(a*cnt-t))//b))
            ans = min(ans,x*cnt + (-((-(a*cnt-t))//b)) * y +  t - (a*cnt - (-((-(a*cnt-t))//b)) * b))
        cnt += 1
else:
    cnt = 0 
    b *= -1
    while cnt * b >=  - 2*10**7:
        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))
            if p_ans != ans:
                print(cnt,ans,y * cnt , ((t - b*cnt)//a) * x , t - (cnt * b  + ((t - b*cnt)//a) * a))
        cnt += 1
print(ans)