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 <iostream>
#include <set>
using namespace std;

int main(int argc, char const *argv[])
{
    long long n, k;
    cin >> n >> k;
    if (k == 1 || n == k)
    {
        cout << 0;
        return 0;
    }
    set<long long> vals;
    if (n > k)
    {
        n %= k;
        vals.insert(n);
    }
    while (true)
    {
        n = abs(n - k);
        //cout << "n is :" << n << endl;
        if (vals.find(n) == vals.end())
            vals.insert(n);
        else
        {
            cout << *vals.begin();
            break;
        }
    }
    return 0;
}