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;
using ll = long long;

#define REP(i, n) for (int i = 0; i < (n); i++)
#define ALL(x) x.begin(), x.end()

ll gcd(ll a, ll b) {
    if (a < b) return gcd(b, a);
    ll r;
    while ((r=a%b)) {
        a = b;
        b = r;
    }
    return b;
}


int main() {
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    
    ll n, k; cin >> n >> k;
    int ans = 0;
    if (n % k == 0) ans = 0;
    else {
        ll g = n % k;
        ans = min(g, abs(g - k));
    }

    cout << ans << endl;

    return 0;
}