$ include "seed7_05.s7i";

const func string: lcs (in string: a, in string: b) is func
  result
    var string: lcs is "";
  local
    var string: x is "";
    var string: y is "";
  begin
    if a <> "" and b <> "" then
      if a[length(a)] = b[length(b)] then
        lcs := lcs(a[.. pred(length(a))], b[.. pred(length(b))]) & str(a[length(a)]);
      else
        x := lcs(a, b[.. pred(length(b))]);
        y := lcs(a[.. pred(length(a))], b);
        if length(x) > length(y) then
          lcs := x;
        else
          lcs := y;
        end if;
      end if;
    end if;
  end func;

const proc: main is func
  begin
    writeln(lcs("thisisatest", "testing123testing"));
    writeln(lcs("1234", "1224533324"));
  end func;