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>

int main()
{
  long N,K,a;
  scanf("%ld%ld",&N,&K);
  a = N-K;
  if (a<0)
    a *= -1;
  if (a > N)
  {
    printf("%ld",N);
    return(0);
  }
  else if (N >= K)
  {
    N %= K;
    a = N - K;
    if (a < 0)
      a *= -1;
    if (a >= N)
    {
      printf("%ld",N);
      return(0);
    }
    else
    {
      printf("%ld",a);
      return (0);
    }
  }
  else
  {
    N = K - N;
    N %= K;
    if (N - K >= N)
    {
      printf("%ld",N);
      return(0);
    }
    else
    {
      printf("%ld",N - K);
      return (0);
    }
  }
}