#!/usr/bin/perl

use strict;
use warnings;
use bigint;

my $n = <>;
my $total = 0;

for(my $i = 0; $i < $n; $i++) {
	my ($c, $d) = split / /, <>;
	my $num = int(($c +1) / 2) * $d;
	$num %= (10**9 + 7);
	$total += $num;
	$total %= (10**9 + 7);
}

print "$total\n";

exit;