#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <tgmath.h>
#include <time.h>
#define ll long long
#define min(a, b) ((a) > (b) ? (b) : (a))
#define max(a, b) ((a) > (b) ? (a) : (b))
#define miin(a, b, c) min((a), min((b), (c)))
#define maax(a, b, c) max((a), max((b), (c)))
#define mod 1000000007

ll n, k;

main()
{
    scanf("%lld%lld", &n, &k);
    printf("%lld\n", miin(n, n % k, k - (n % k)));
    return 0;
}