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 <iomanip>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <unordered_map>
#include <cmath>
using namespace std;

typedef unsigned int uint;
typedef long long llong;
typedef unsigned long long ullong;
// -2.1e-9 <= int <= 2.1e9
// -9.2e-18 <= long long <= 9.2e18
// 0 <= unsigned int <= 4.2e9
// 0 <= unsigned long long <= 18.4e18

int main()
{
    llong N, K;
    cin >> N >> K;
    if (N < K) {
        llong Nmin1 = abs(N - K);
        // int ans = min(N, Nmin1);
        llong ans;
        if (N < Nmin1) ans = N;
        else ans = Nmin1;
        cout << ans << endl;
        return 0;
    }
    llong Nmin1 = N % K;
    llong Nmin2 = abs(Nmin1 - K);
    llong ans;
    if (Nmin1 < Nmin2) ans = Nmin1;
    else ans = Nmin2;
    cout << ans << endl;

}