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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
int main()
{
  long long int N, K;
  long long int min;
  long long int a;
  cin >> N >> K;
  min = N;
  if (N < K)
  {
    cout << N << endl;
  }
  else if (N == K)
  {
    cout << 0 << endl;
  }
  else
  {
    long long int s;
    s = N / K;
    //cout << s << endl;
    for (long long int i = s;; i++)
    {
      a = abs(N - (K * i));
      //cout << a << endl;
      if (a == 0)
      {
        cout << 0 << endl;
        return 0;
      }
      else if (a > min)
      {
        cout << abs(N - K * (i - 1)) << endl;
        return 0;
      }
      min = a;
    }
  }
}