power_stage_square.msp

even : (int) => bool = 
  lambda x.
    x % 2 == 0 
      
square : (<int>) => <int> = 
  lambda x.
    x * x

power : (<int>, int) => <int> = 
  lambda x n.
    if n == 0
      then 1
      else 
        if even(n)
          then square(power(x, n / 2))
          else x * power(x, n - 1)

main : <(int) => int> = 
  lambda input.
    power(input, 13)