Решение задачи File 51

program File51;
var
 S1,S2,S3,S4: String;
 F1,F2,F3,F4: File of Real;
 El1,El2,El3:Real;
 File1end,File2end,File3end:boolean;
Function comparison(A,B,C:Real; Ba,Bb,Bc:Boolean): Boolean;
begin
 if not(Ba) and not(Bb) and not(Bc) then
  if (A>=B) and (A>=C) then comparison:=true
  else comparison:=false
 else
  if not(Ba) and not(Bb) and Bc then
   if (A>=B) then comparison:=true
   else comparison:=false
  else
   if not(Ba) and Bb and not(Bc) then
    if (A>=C) then comparison:=true
    else comparison:=false
   else
    if not(Ba) and Bb and Bc then comparison:=true
    else comparison:=false;
end;
begin
  Write('S1: ');
  Readln(S1);
  Write('S2: ');
  Readln(S2);
  Write('S3: ');
  Readln(S3);
  Write('S4: ');
  Readln(S4);
  Assign(F1,S1);
  Assign(F2,S2);
  Assign(F3,S3);
  Assign(F4,S4);
  Reset(F1);
  Reset(F2);
  Reset(F3);
  ReWrite(F4);
  Read(F1,El1);
  Read(F2,El2);
  Read(F3,El3);
  File1end:=false;
  File2end:=false;
  File3end:=false;
  while (not (File1end) or not(File2end) or not(File3end)) do
   begin
    if comparison(El1,El2,El3,File1end,File2end,File3end) then
     begin
      Write(F4,El1);
      if not(eof(F1)) then Read(F1,El1)
      else File1end:=true;
     end
    else
     if comparison(El2,El1,El3,File2end,File1end,File3end) then
      begin
       Write(F4,El2);
       if not(eof(F2)) then Read(F2,El2)
       else File2end:=true;
      end
     else
      if comparison(El3,El1,El2,File3end,File1end,File2end) then
       begin
        Write(F4,El3);
        if not(eof(F3)) then Read(F3,El3)
        else File3end:=true;
       end;
   end;
  Close(F1);
  Close(F2);
  Close(F3);
  Close(F4);
  Readln;
end.