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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main(void){
	unsigned long int N, K;
	unsigned long int min_bif, min_now;
	int min;

	scanf("%d %d", &N, &K);

	N = N % K;	
	min_bif = N;
	while (1) {
		if ( N > K ) {
			N = N-K;
			min_now = N;
		} else {
			N = K-N;
			min_now = N;
		}
		printf("bif:%d  now:%d\n", min_bif, min_now);
		if (min_bif <= min_now) { 
			min = min_bif;
			break;
		} else {
			min_bif = min_now;
		}
	}

	printf("%d\n", min);

	return 0;
}