#! /usr/bin/perl -w 
use strict;

my $sum_x = 0;
my $sum_y = 0;
my $sum_x2 = 0;
my $sum_xy = 0;
my $n = 0;


while( <> ) {
	my ( $x, $y ) = split;
	
	$sum_x += $x;
	$sum_y += $y;
	$sum_x2 += $x * $x;
	$sum_xy += $x * $y;
	$n++;
	
}

my $a = ( $sum_y * $sum_x2 - $sum_x * $sum_xy ) /
	          ( $n * $sum_x2 - $sum_x * $sum_x );  
my $b =     ( $n * $sum_xy - $sum_x * $sum_y ) /
	          ( $n * $sum_x2 - $sum_x * $sum_x );  

print "a = $a; b = $b\n";