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 9.2.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main()
{
    unsigned long long int n, k;
    long long int tmp;
    int end;

    scanf("%llu%llu", &n, &k);

    if (k == 1)
        n = 0;
    else {
        do {
            end = 0;
            tmp = n - 10000 * k;
            if (tmp > 0) {
                n = tmp;
                end = 1;
            }
        } while (end == 1);
        
        do {
            end = 0;
            tmp = (long long int)(n - k);
            if (tmp < 0)
                tmp *= -1;
            if (tmp < n) {
                n = (unsigned long long)tmp;
                end = 1;
            }
        } while (end == 1);
    }

    printf("%llu\n", n);

    return 0;
}