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: Time Limit Exceeded)

#include <stdio.h>

long int absolute(long int *n,long int *k){
	return (*n-*k > 0) ? (*n-*k) : (*k-*n);
}
int main(){
	long int N,K;
	long int pre;
	long int cur;
	scanf("%ld%ld",&N,&K);
	
	pre = absolute(&N,&K);
	cur = absolute(&N,&K);
	
	
	while(1){
		if(K == 1){
			cur=0;
			break;
		}
		if(K == 0){
			break;
		}
		cur=absolute(&pre,&K);
		if(pre<cur){
			cur = pre;
			break;
		}
		pre=cur;
			
	}
	printf("%ld\n",cur);
	
	return 0;
}