print " Enter the number. \n";
 chomp ($df = <STDIN>);
 open FILE, "45well.txt" or die $!;
 while (<FILE>){
 chomp $_;
  @values = split('\t', $_);
   foreach $val (@values){
   $DNA_conc = $val * $df * 50 ;
 print $DNA_conc;
 print"\t";
 }
 }
  print "\n";
 close (FILE);