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: Time Limit Exceeded)

#include<bits/stdc++.h>
using namespace std;
long inf = 1000000007;

int main() {
	long n, k; cin >> n >> k;
	if (n == 0 || k == 1) {
		cout << 0 << endl;
	}
	else {
		while (n > abs(n - k)) {
		
		while (abs(n - k) > 1024000000 * k) {
			n = abs(n - 1024000000 * k);
		}
		while (abs(n - k) > 102400000 * k) {
			n = abs(n - 102400000 * k);
		}
		while (abs(n - k) > 10240000 * k) {
			n = abs(n - 10240000 * k);
		}
		while (abs(n - k) > 1024000 * k) {
			n = abs(n - 1024000 * k);
		}
		while (abs(n - k) > 102400 * k) {
			n = abs(n - 102400 * k);
		}
		while (abs(n - k) > 10240 * k) {
			n = abs(n - 10240 * k);
		}
		while (abs(n - k) > 1024 * k) {
			n = abs(n - 1024 * k);
		}
		while (abs(n - k) > 512 * k) {
			n = abs(n - 512 * k);
		}
		while (abs(n - k) > 256 * k) {
			n = abs(n - 256 * k);
		}
		while (abs(n - k) > 128 * k) {
			n = abs(n - 128 * k);
		}
		while (abs(n - k) > 64 * k) {
			n = abs(n - 64 * k);
		}
		while (abs(n - k) > 32 * k) {
			n = abs(n - 32 * k);
		}
		while (abs(n - k) > 16 * k) {
			n = abs(n - 16 * k);
		}
		while (abs(n - k) > 8 * k) {
			n = abs(n - 8 * k);
		}
		while (abs(n - k) > 4 * k) {
			n = abs(n - 4 * k);
		}
		while (abs(n - k) > 2 * k) {
			n = abs(n - 2 * k);
		}
			n = abs(n - k);
		}

		cout << n << endl;
	}
	
}