(define (square x) (* x x))
(display
  (let powmod ((x (read)) (e (read)) (m (read)))
    ; let's ignore negative e here
    (cond ((= e 0) 1)
          ((= e 1) (remainder x m))
          ((even? e) (remainder (square (powmod x (/ e 2) m)) m))
          (else (remainder (* (square (powmod x (quotient e 2) m)) x) m)))))
(newline)