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 _GLIBCXX_DEBUG
#define rep2(i, m, n) for(int i=int(m); i<int(n); ++i)
#define drep2(i, m, n) for(int i=int(m-1); i>=int(n); --i)
#define rep(i, n) rep2(i, 0, n)
#define drep(i, n) drep2(i, n, 0)
#define all(a) a.begin(), a.end()
#define fst first
#define snd second
using ll = long long;
using ld = long double;
using V = vector<int>;
using Vll = vector<ll>;
using Vld = vector<ld>;
using Vbo = vector<bool>;
using VV = vector<V>;
using VVll = vector<Vll>;
using VVld = vector<Vld>;
using VVbo = vector<Vbo>;
using P = pair<int, int>;
using Pll = pair<ll, ll>;
using Pld = pair<ld, ld>;
template<typename T> inline bool chmin(T& a, T b) {if(a>b) {a=b; return true;} return false;}
template<typename T> inline bool chmax(T& a, T b) {if(a<b) {a=b; return true;} return false;}
inline int Log2(ll x) {int k; for(k=0; x>0; ++k) x>>=1; return k;} // number of binary digits
template<typename T> inline int count_between(vector<T>& a, T l, T r) {
  return lower_bound(all(a), r) - lower_bound(all(a), l); // [l, r)
}
template<typename T> istream& operator>>(istream& is, vector<T>& v) {
  rep(i, v.size()) is >> v[i]; return is;
}
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v) {
  rep(i, v.size()) os << v[i] << " "; return os;
}
const int INF  = 1<<30;
const ll INFll = 1ll<<62;
const ld EPS   = 1e-10;
const int MOD  = int(1e9)+7;


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

  ll ans;
  ll m = n % k;
  if (m <= k/2) ans = m;
  else ans = abs(m-k);

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