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;
string to_string(const string& s) {
	return '"' + s + '"';
}
string to_string(const bool b) {
	return (b ? "true" : "false");
}
string to_string(const char* s) {
	return to_string((string)s);
}
string to_string(const char c) {
	string s = "'";
	s += c;
	s += "'";
	return s;
}
template<class T, class U>
string to_string(const pair<T, U>& p) {
	string s = "(";
	s += to_string(p.first);
	s += ", ";
	s += to_string(p.second);
	s += ")";
	return s;
}
template<class T>
string to_string(const T& a) {
	bool first = true;
	string s = "{";
	for (const auto& x : a) {
		if(!first){
			s += ", ";
		}
		first = false;
		s += to_string(x);
	}
	s += "}";
	return s;
}
void debug_out() {cerr << '\n';}
template<class Head, class... Tail>
void debug_out(Head head, Tail... tail) {
	cerr << ' ' << to_string(head);
	debug_out(tail...);
}
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "] = ", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif
using ll = long long;
using ld = long double;
const int mod = 1e9 + 7;
const int inf = 1e9 + 100;
const ll inf64 = 7e18l;
int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(20);
	ll n, k;
	cin >> n >> k;
	while (n < k) {
		n += n;
	}
	cout << min(n % k, k - n % k) << '\n';
 	return 0;
}