import math
t=int(input())
x,a=list(map(int,input().split()))
y,b=list(map(int,input().split()))
def f(time):
    if time>0:
        n=time%a
        for i in range(n//x):
            m=n+i*x
            n=min(n,(m//b)*y+m%b)
        print(n+(time//a)*x)
    elif t<0:
        u=abs(time)
        r=(math.ceil(u/b))
        return(r*y+f(r*b-u))
    else:
        return(0)
print(f(t))