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 <math.h>

int main (void) {
  long int N, K;
  long int x, x1, xmin, befxmin;

  scanf("%d %d", &N, &K);
  x = N;
  xmin = N;
  befxmin = N;

  if (K != 1) {
    while (1) {
      x1 = fabs(x - K);
      if (x1 < x) {
	xmin = x1;
      }
      x = x1;
      if (xmin >= befxmin) {
	break;
      } else {
	befxmin = xmin;
      }
    }
    printf("%ld\n", xmin);
  } else {
    printf("0\n");
  }
  
  return 0;
}