Решение задачи File 48

# -*- coding: utf-8 -*-
import sys

lst_file = ["file48_1.txt", "file48_2.txt", "file48_3.txt", "file48_4.txt"]
f_output = "file48_all.txt"

try:
    f_in = []
    for f_input in lst_file:
        f_in.append(open(f_input, "r"))

    flag = True
    with open(f_output, "w") as f_out:
        while flag:
            for f in f_in:
                line = f.readline()
                if not line:
                    flag = False
                    break
                print(line)
                f_out.write(line.strip()+"\n")

    for f in f_in:
        f.close()
        
except:
    print("Error: ", sys.exc_info())
									

program File48;
var
 SA,SB,SC,SD: String;
 FA,FB,FC,FD :File of Integer;
 El:Integer;
begin
  Write('SA: ');
  Readln(SA);
  Write('SB: ');
  Readln(SB);
  Write('SC: ');
  Readln(SC);
  Write('SD: ');
  Readln(SD);
  Assign(FA,SA);
  Reset(FA);
  Assign(FB,SB);
  Reset(FB);
  Assign(FC,SC);
  Reset(FC);
  Assign(FD,SD);
  Rewrite(FD);
  while not Eof(FA) do
   begin
    Read(FA,El);
    Write(FD,El);
    Read(FB,El);
    Write(FD,El);
    Read(FC,El);
    Write(FD,El);
   end;
  Close(FA);
  Close(FB);
  Close(FC);
  Close(FD);
end.