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(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)
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