#!/usr/bin/perl
use warnings;
use strict;

open my $IN,   '<', 'input.txt'  or die "Can't open 'input.txt' $!";
open my $FILE, '>', 'output.txt' or die "Can't open 'output.txt' $!";

my $previous = -1;
my @data;
while ( <$IN> ) {
        my ( $n, $p ) = split;
        no warnings qw/ numeric uninitialized /;
        if ( $n == $previous + 1 ) {
                push @data, $p
                }
        else {
                print $FILE "$data[0]\t$data[-1]\t", scalar @data, "\n" if @data > 1;
                @data = $p;
                }
        $previous = $n;
        }

__END__