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: Time Limit Exceeded)

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

int main(void)
{
  char buf[1000];
  long n, k, now, before;

  fgets(buf, sizeof(buf), stdin);
  sscanf(buf, "%ld %ld\n", &n, &k);

  before = n;

  while (1) {
    if (k == 1) {
      before = 0;
      break;
    }

    now = labs(n - k);

    if (now < before) {
      before = now;
      n = now;
    } else {
      break;
    }
  }

  printf("%ld\n", before);

}