a1, b1 = map(int, input().split())
a2, b2 = map(int, input().split())
a3, b3 = map(int, input().split())

def ext_gcd(a, b):
  if b==0:
    return a, 1, 0
  d, p, q = ext_gcd(b, a%b)
  p, q = q, p-a//b*q
  return d, p, q

def chinese_remainder(a1, b1, a2, b2):
  if a1<0: return -1, -1
  d, p, q = ext_gcd(b1, b2)
  if a1%d!=a2%d: return -1, -1
  t = b1*b2//d
  s = (a2-a1)//d
  return (a1+s*b1*p)%t, t

a1, b1 = chinese_remainder(a1, b1, a2, b2)
a1, b1 = chinese_remainder(a1, b1, a3, b3)


if a1<0: print(-1)
else: print(a1)