T = int(input())
X, A = map(int, input().split())
Y, B = map(int, input().split())
ans = 10 ** 15 + 1
tmp = 10 ** 15
y = max(-(T//B),0)
i = 0
ans = tmp
x = (T + B * y) // A
d = T - A * x + B * y
tmp = X * x + Y * y + d
ans = min(ans,tmp)
#print(x, y, d, ans, tmp)
while i < 10:
    if X > Y:
        x += 1
        y = - ((T - A * x) // B)
        d = T - A * x + B * y
    else:
        y += 1
        x = (T + B * y) // A
        d = T - A * x + B * y
    tmp = X * x + Y * y + d
    ans = min(ans, tmp)
    #print(x, y, d, ans, tmp)
    i += 1
print(ans)