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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>
#include<math.h>

long long get(long long n,long long k){
  long long ans1,ans2;
  long long q,r;

  if(k == 0) return n;

  q = n % k;
  if(q == 0) return 0;

  r = n/k;
  if(n < k) r = 0;

  ans1 = (long long)abs(n - r*k);
  ans2 = (long long)abs(ans1 - k);

  if(ans1 < ans2) return ans1;

  else return ans2;
}

int main(){
  long long n,k;

  scanf("%lld %lld", &n, &k);

  printf("%lld\n", get(n,k));

  return 0;
}