t = int(input())
x,a = map(int,input().split())
y,b = map(int,input().split())
ans = float("inf")
if t >= 0:
  for i in range(t+1):
    back = b*i
    z = t+back
    ans = min(ans, y*i+(z//a)*x + z%a)
else:
  t *= -1
  for i in range(10**7):
    fwd = a*i
    if fwd > 10**7: break
    z = t + fwd
    ans = min(ans, y*((z+b-1)//b) + b*((z+b-1)//b)-z)
    

print(ans)