R>S>P>Q
P+R>Q+S .(1)
Q+R=P+S .(2)
(1)-(2)得:P-Q>Q-P,则P>Q
(1)+(2)得:P+Q+2R >Q+P+2S,则R>S
再考虑S>P,则可排出:R>S>P>Q