Problem:
Score : 300 points

Problem Statement

Given any integer x, Aoki can do the operation below.

Operation: Replace x with the absolute difference of x and K.

You are given the initial value of an integer N. Find the minimum possible value taken by N after Aoki does the operation zero or more times.

Constraints

0 ≤ N ≤ 10^{18}

1 ≤ K ≤ 10^{18}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the minimum possible value taken by N after Aoki does the operation zero or more times.

Sample Input 1

7 4

Sample Output 1

1

Initially, N=7.

After one operation, N becomes |7-4| = 3.

After two operations, N becomes |3-4| = 1, which is the minimum value taken by N.

Sample Input 2

2 6

Sample Output 2

2

N=2 after zero operations is the minimum.

Sample Input 3

1000000000000000000 1

Sample Output 3

0

Solution in Perl (v5.18.2) (judge verdict: Accepted)

#!/usr/bin/perl

my ($N,$K) = map { $_ - 0 } split(/\s+/,<STDIN>);

if( $N == $K ){
  print "0\n";
  exit(0);
}

my $oN = $N;

if( $N > $K ){
  my $d = $N - $K;
  my $d2 = $d % $K;
  if( $d2 == 0 ){
    print "0\n"; exit(0);
  }
  my $d3 = $d - $d2;
  $N -= $d3;
}

my $mn = $N;

for(my $i=0;$i<15;$i++){
  $N = abs($K - $N);
  $mn = $N if $N < $mn;
}

$mn = $oN if $oN < $mn;

print "$mn\n";