#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using VI = vector<int>;
using VL = vector<ll>;
using VS = vector<string>;
using VVI = vector<vector<int>>;
using VVL = vector<vector<ll>>;
using PII = std::pair<int, int>;
using PLL = std::pair<ll, ll>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
#define rep3(i, s, n, d) for (int i = (s); i < (int)(n); i += (d))
#define allpt(v) (v).begin(), (v).end()
#define allpt_c(v) (v).cbegin(), (v).cend()
#define allpt_r(v) (v).rbegin(), (v).rend()

const int mod = 1e9 + 7, mod2 = 998244353, mod3 = 1e9 + 9;
const ll inf = 1e18;

const string wsp = " ";
const string tb = "\t";
const string rt = "\n";

template <typename T>
void show1dvec(const vector<T> &v)
{
    if (v.size() == 0)
        return;
    int n = v.size() - 1;
    rep(i, n) cout << v[i] << wsp;
    cout << v[n] << rt;
    ;
    return;
}

template <typename T>
void show2dvec(const vector<vector<T>> &v)
{
    int n = v.size();
    rep(i, n) show1dvec(v[i]);
}

template <typename T, typename S>
void show1dpair(const vector<pair<T, S>> &v)
{
    int n = v.size();
    rep(i, n) cout << v[i].first << wsp << v[i].second << rt;
    return;
}

template <typename T, typename S>
void pairzip(const vector<pair<T, S>> &v, vector<T> &t, vector<T> &s)
{
    int n = v.size();
    rep(i, n)
    {
        t.push_back(v[i].first);
        s.push_back(v[i].second);
    }
    return;
}

template <typename T>
void maxvec(vector<T> &v)
{
    T s = v[0];
    int n = v.size();
    rep(i, n - 1)
    {
        if (s > v[i + 1])
        {
            v[i + 1] = s;
        }
        s = v[i + 1];
    }
}

template <typename T, typename S>
bool myfind(T t, S s)
{
    return find(t.cbegin(), t.cend(), s) != t.cend();
}

bool check(int y, int x, int h, int w)
{
    return 0 <= y && y < h && 0 <= x && x < w;
}

VL cumsum(const VL &v)
{
    int s = 0;
    VL ret = {0};

    rep(i, v.size())
    {
        s += v[i];
        ret.push_back(s);
    }
    return ret;
}

bool iskadomatsu(int a, int b, int c)
{
    return (a != b && b != c && c != a) && ((a > b && b < c) || (a < b && b > c));
}

void shave(vector<int> &v, int k, int n)
{
    vector<int> x, y;
    int n_sq = sqrt(n) + 1;
    for (int i = 3; i < n + 1; i += 2)
    {
        x.push_back(i);
    }
    for (int i = 3; i < n_sq; i += 2)
    {
        for (auto itr = x.cbegin(); itr != x.cend(); itr++)
        {
            if (*itr == i || *itr % i != 0)
                y.push_back(*itr);
        }
        x.clear();
        x = y;
        y.clear();
    }

    if (n >= 2 && k <= 2)
        v.push_back(2);
    for (auto itr = x.cbegin(); itr != x.cend(); itr++)
    {
        if (*itr >= k)
            v.push_back(*itr);
    }
}

VI dag1(int n, const VVI &connect, VI indeg, VI &initial)
{
    VI order;
    VI search, new_search;
    rep(i, n) if (!indeg[i]) search.push_back(i), initial.push_back(i);

    order = initial;
    while (!search.empty())
    {
        for (int i : search)
        {
            rep(j, n)
            {
                if (connect[i][j] != -1)
                {
                    indeg[j]--;
                    if (!indeg[j])
                        new_search.push_back(j), order.push_back(j);
                }
            }
        }
        search.clear();
        search = new_search;
        new_search.clear();
    }
    reverse(allpt(order));
    return order;
}

void dag2(int n, const VVI &connect, VI order, const VI &initial)
{
    VI dp(n, 0), ans(n, 0);
    dp[order[0]] = 1;
    for (int i : order)
    {
        rep(j, n)
        {
            if (connect[j][i] != -1)
                dp[j] += dp[i] * connect[j][i];
        }
    }
    for (int z : initial)
        ans[z] = dp[z];
    rep(i, n - 1) cout << ans[i] << rt;
};



int main()
{

#ifdef DEBUG
    cout << "DEBUG MODE" << endl;
    ifstream in("input.txt"); //for debug
    cin.rdbuf(in.rdbuf());    //for debug
#endif

    ll n, k; cin >> n >> k;
    cout << min((n % k), k - (n % k)) << rt;


    return 0;
}


Measured memory_bytes: 256