a,b=map(int, input().split())
c,d=map(int, input().split())
e,f=map(int, input().split())
import math
def egcd(a, b):
    if a == 0:
        return b, 0, 1
    else:
        g, y, x = egcd(b % a, a)
        return g, x - (b // a) * y, y
def chineseRem(b1, m1, b2, m2):
    # 中国剰余定理
    # x ≡ b1 (mod m1) ∧ x ≡ b2 (mod m2) <=> x ≡ r (mod m)
    # となる(r. m)を返す
    # 解無しのとき(0, -1)
    d, p, q = egcd(m1, m2)
    if (b2 - b1) % d != 0:
        return 0, -1
    m = m1 * (m2 // d)  # m = lcm(m1, m2)
    tmp = (b2-b1) // d * p % (m2 // d)
    r = (b1 + m1 * tmp) % m
    return r, m
x,y=chineseRem(a,b,c,d)
if x==0 and y==-1:
  print(-1)
  exit()
for i in range(10**6):
  d=i*y+x
  if d%f==e and d>0:
    print(d)
    exit()
print(-1)