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: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(){
    unsigned long long n,k,mod,ans=0,tmp;
    char token[300000]={};
    fgets(token, sizeof(token), stdin);
    n=atoll(strtok(token, " "));k=atoll(strtok(NULL, " "));
    if (n>=k) {
        mod=n%k;
        tmp=k-mod;
        if (tmp<mod) ans=tmp;
        else ans=mod;
    }else{
        tmp=k-n;
        if (tmp<n) ans=tmp;
        else ans=n;
    }
    printf("%lld",ans);
    return 0;
}