2001 AIME II Problem 3

Given that

$$\begin{aligned}& x_{1}=211 \& x_{2}=375 \& x_{3}=420 \& x_{4}=523, \text { and } \& x_{n}=x_{n-1}-x_{n-2}+x_{n-3}-x_{n-4} \text { when } n \geq 5\end{aligned}$$

find the value of x_{531}+x_{753}+x_{975}.