/*

a * x + b * y = gcd(a, b)

a / gcd(a, b) * x + b / gcd(a, b) * y = 1

令 A = a / gcd(a, b) 
   B = b / gcd(a, b)

则 A * x + B * y = 1
注意: gcd(A, B) = 1

A * (x + B) + B * y = 1
令 X = x + B, Y = y

则: A * X + B * Y = 1
未知数还是未知数,不影响;

a * x + b * y = c * gcd(a, b) (同理)



*/