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: Accepted)

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define all(container) container.begin(),container.end()
#define fast ios::sync_with_stdio(0); cin.tie(0)
// #ifndef ONLINE_JUDGE
// #include "debug.cpp"
// #endif
#define int long long
const int mod = 1e9+7;  
int power(int a,int b) { if(b==0) return 1; int res = power(a,b/2); if(b&1) return res * res * a; else return res * res; }


int32_t main(){
    
  fast;
  int n,k; cin >> n >> k;

  if(n<k){
    cout << min(n,abs(n-k));
  }
  else{
    
    int x = n/k;

    if(n%k==0){
      cout << 0;
    }else{
      int a = x - 1;
      int b = x;
      int c = x + 1;
      vector<int> ans;
      ans.pb(abs(n - a*k));
      ans.pb(abs(n - b*k));
      ans.pb(abs(n - c*k));
      sort(all(ans));
      cout << ans[0];
    }
  }

  return 0;
}