[[Problem 1340]] -f(X,Y,Z):YYZXXXYY f(,f(rf(,f(s,,),),f(f(,s,rsl),,)f(f(,s,lsr),r,),),) -- mas &new{2013-02-23 (土) 09:06:27}; -a(X):XXXrr b(X):a(ssXss) a(a(a(a(b(rsl)b(lsr)))a()b()r)a()) -- Ktya &new{2013-02-23 (土) 11:36:04};