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>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main() {
  ll n, k;
  cin >> n >> k;

  ll ans = n;
  while (true) {
    if (n == 1) {
      cout << 1 << endl;
      return 0;
    } else if (n == k) {
      cout << 0 << endl;
      return 0;
    } else if (n > k) {
      n %= k;
      if (n == 0) {
        cout << 0 << endl;
        return 0;
      }
      ans = min(ans, n);
    } else {
      if (n < k/2){
        cout << ans << endl;
        return 0;
      } else{
        cout << min(ans, k -n) << endl;
        return 0;
      }
    }
  }

  cout << ans << endl;
  return 0;
}