use strict;
use warnings;

my $input = "input.txt";
open my $IN, "<", $input or die "cannot open $input $!";
my $output = "output.txt";
open my $OUT, ">", $output or die "cannot open $output $!";
while (my $line = <$IN>) {
    chomp $line; # remove newline character from end of line
    if ($line =~ /INTERPOLATED HYDROGRAPH AT (\w+)$/){
        print $OUT $1;
        $line = <$IN> for 1..6; # skip 5 lines
        my $val2 = (split / /, $line)[1]; # get the second column
        print $OUT " $val2";
        $line = <$IN>for 1..2; # skip one line
        chomp $line;
        my $val3 = (split / /, $line)[-1]; # get the last column
        print $OUT " $val3\n"; 
    }
}