/* 

  Enigma 1021: All at threes and sevens in Picat.

  From https://enigmaticcode.wordpress.com/2019/03/01/enigma-1021-all-at-threes-and-sevens/#comments
  """
  For his work in detention, Johnny was set to multiply two large numbers together. One number consisted 
  entirely of threes, the other entirely of sevens:

    3333… × 7777… = ???

  Surprisingly, he managed to get the correct answer. When he examined his answer he noticed that it 
  contained exactly 7 sevens and 3 threes.

  How many digits were there altogether in Johnny’s answer?
  """

  This Picat model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/


import util.

main => go.


go =>
  Found = false,
  foreach(Len3 in 10..100, Len7 in 10..100, Found = false)
    Three = [3.to_string() : _ in 1..Len3].join('').to_int,
    Seven = [7.to_string() : _ in 1..Len7].join('').to_int,
    Result = (Three * Seven).to_string(),
    if [1 : D in Result, D = '3'].len == 3, [1 : D in Result, D = '7'].len == 7 then
      println(len=Result.len),
      Found := true
    end
  end,
  nl.


%%
%% Misusing CP count/2.
%% Slower.
%%
% go2 =>
%   Found = false,
%   foreach(Len3 in 10..100, Len7 in 10..100, Found = false)
%     Three = [3.to_string() : _ in 1..Len3].join('').to_int,
%     Seven = [7.to_string() : _ in 1..Len7].join('').to_int,

%     Result = (Three * Seven),
%     ResultIntList = [I.to_int() : I in Result.to_string()],
%     C3 #= count(3,ResultIntList),
%     C7 #= count(7,ResultIntList),
%     if C3 #= 3, C7 #= 7 then
%       println([Three,Seven,Result]),
%       println(len=ResultIntList.len),
%       Found := true
%     end
%   end,
%   nl.