def gcd(A,B):
    if B<A:
        return gcd(B,A)
    if B%A==0:
        return A
    return gcd(B%A,A)

X1,Y1=map(int,raw_input().split())
X2,Y2=map(int,raw_input().split())
X3,Y3=map(int,raw_input().split())

A1,B1=X1,Y1
if A1==0:
    A1+=Y1
for i in range(Y2):
    if A1%Y2==X2:
        break
    A1+=B1
if A1%Y2!=X2:
    print -1
    exit()
else:
    B1/=gcd(B1,Y2)
    B1*=Y2

for i in range(Y3):
    if A1%Y3==X3:
        break
    A1+=B1

if A1%Y3==X3:
    print A1
else:
    print -1