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 9.2.1) (judge verdict: Wrong Answer)

#include <iostream>
#include <stdlib.h>
using namespace std;

int main() {
  long long N, K;
  cin >> N >> K;
  
  //Nが0だったらKを出力
  if (N==0) {
    cout << K << endl;
    return 0;
  //NがKで割り切れるなら最小値は0
  } else if ((N%K)==0) {
    cout << 0 << endl;
    return 0;
  }
  
  long long llbuff=1000000000000000000;
  while(1) {
    //0は最小
    if (N==0) {
      break;
    } else if (N>llbuff) {
      N = llbuff;
      break;
    }
    llbuff = N;
    if (N < K) {
      N = K - N;
    } else {
      N = N - K;
    }
  }
  
  cout << N << endl;
    
  return 0;
}