(define (square x) (* x x))

(define (f x y z)
   (cond ((and (< x y) (< x z)) (+ (square y) (square z)))
         ((and (< y x) (< y z)) (+ (square x) (square z)))
         (else (+ (square x) (square y)))))

(= 13 
  (f 1 2 3)
  (f 1 3 2)
  (f 2 1 3)
  (f 2 3 1)
  (f 3 1 2)
  (f 3 2 1))