$ include "seed7_05.s7i";
  include "bigint.s7i";

const func bigInteger: digitalRoot (in var bigInteger: num, in bigInteger: base, inout bigInteger: persistence) is func
  result
     var bigInteger: sum is 0_;
  begin
    persistence := 0_;
    while num >= base do
      sum := 0_;
      while num > 0_ do
        sum +:= num rem base;
        num := num div base;
      end while;
      num := sum;
      incr(persistence);
    end while;
  end func;

const proc: main is func
  local
    var bigInteger: num is 0_;
    var bigInteger: root is 0_;
    var bigInteger: persistence is 0_;
  begin
    for num range [] (627615_, 39390_, 588225_, 393900588225_) do
      root := digitalRoot(num, 10_, persistence);
      writeln(num <& " has additive persistence " <& persistence <& " and digital root of " <& root);
    end for;
  end func;