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>
#include<math.h>
int main()
{
    long long n,k,m,d;
    scanf("%lld%lld",&n,&k);
    if(n==0||k==1) { printf("0\n");return 0; }
    if(n%2==0&&k%2==0&&n>=k) { printf("0\n");return 0; }
    if(n==k) { printf("0\n");return 0; }
    if(n%2==1&&k%2==1&&n>=k) { printf("1\n");return 0; }
    if(n>k){
        m=n%k;
        d=fabs(m-k);
        if(d<m)
            m=d;
        printf("%lld\n",m);
        return 0;
    }
    m=0;
    while(n>m){
        n=fabs(n-k);
        m=fabs(n-k);
    }
    d=fabs(m-k);
    if(d<m)
        m=d;
    printf("%lld\n",m);
    return 0;
}