/* aman36 - Aman Raj */

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
 
#define IOS ios :: sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define AfterDecimal(n) cout << fixed << setprecision(n);
#define pb push_back
#define pp(a, b) pair <a, b>
#define ll long long
#define ld long double
#define all(a) a.begin(), a.end()
#define pi pair<int, int>
#define pll pair<ll, ll>
#define F first
#define S second
#define itr iterator
#define bits(x) __builtin_popcount(x)
#define fori(n)  for (ll i = 0; i < n; i++)
#define forj(n)  for (ll j = 0; j < n; j++)
#define fork(n)  for (ll k = 0; k < n; k++)
#define forlp(k,x,n)  for (ll k = x; k <= n; k++)
#define vll vector <ll>
#define mll map <ll, ll>
#define vpll vector <pll>
#define mem(x) memset(x, 0, sizeof(x));
#define int ll
#define endl "\n"
 
using namespace __gnu_pbds;
using namespace std;
 
template <class T> T printr(T p) { cout << p << '\n'; return 0; }
template <class T> T printe(T p) { cout << p << '\n'; exit(0); }
template <class T> bool uin(T &a, T b) { return a > b ? (a = b, true) : false; }
template <class T> bool uax(T &a, T b) { return a < b ? (a = b, true) : false; }
 
template <typename T> using ordered_set =
 tree<T, null_type, less<T>, rb_tree_tag, 
 tree_order_statistics_node_update>;
 
#ifdef DEBUG
#define debug(...) __f(#__VA_ARGS__, __VA_ARGS__)
template<typename Arg1>
void __f(const char* name, Arg1&& arg1){
    cout << "# "<< name << " = " << arg1 << '\n';
}
template<typename Arg1, typename... Args>
void __f(const char* names, Arg1 && arg1, Args &&... args){
        const char* comma = strchr(names + 1 ,',');
        cout << "# ";
        cout.write(names, comma - names)<< " = " << arg1 << " | ";
        __f(comma + 1, args...);
}
#else
#define debug(...) 36
#endif

ll power(ll x, ll y, ll p) { 
    ll res = 1;
    x = x % p;  
    while (y > 0) {
        if (y & 1) 
            res = (res * x) % p; 
        y = y >> 1;
        x = (x * x) % p; 
    }
    return res;
}

bool isPrime(int n) 
{ 
    if (n <= 1) return false; 
    if (n <= 3) return true; 
    if (n % 2 == 0 || n % 3 == 0) return false;  
    for (int i = 5; i * i <= n; i = i + 6) 
        if (n % i == 0 || n % (i + 2) == 0) 
            return false; 
    return true; 
}


const ll INF = (ll)(8e18);
const ll MOD = 1e9 + 7;
const ll MOD2 = 998244353;
const int M = 1000+5;
const int maxn = 1e4+5;
// check the limits

int fun(int a, int b, char ch) {
    if(ch == '&') {
        int s[4][4] = {{0, 0, 0, 0},{0, 1, 2, 3},{0, 2, 2, 0},{0, 3, 0, 3}};
        return s[a][b];
    }
    if(ch == '|') {
        int s[4][4] = {{0, 1, 2, 3},{1, 1, 1, 1},{2, 1, 2, 1},{3, 1, 1, 3}};
        return s[a][b];
    }
    if(ch == '^') {
        int s[4][4] = {{0, 1, 2, 3},{1, 0, 3, 2},{2, 3, 0, 1},{3, 2, 1, 0}};
        return s[a][b];
    }
    return 0;
}

void solve() {
    int n, k;
    cin >> n >> k;

    n = n%k;
    if(abs(n-k) < n) {
        n = abs(n-k);
    }

    cout << n << endl;
}

int32_t main() {
    IOS;
    #ifndef ONLINe5E_JUDGE
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    #endif

    int t;
    t = 1;
    for(int tc=1; tc<=t; tc++) {
        // cout << "Case #" << tc << ": ";
        solve();
    }

    #ifdef LOCAL
    cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
    #endif
}

/* g++ -DLOCAL -DDEBUG -std=c++17 -Wshadow -Wall -o "c" "icpc.cpp" 
-fsanitize=address -fsanitize=undefined -D_GLIBCXX_DEBUG -g */

// read the question correctly
// read code carefully
// corner cases // int vs ll // cin vs scanf // clear structures // maths
// check max, min set to INT_MAX instead INF
// check constraints

Measured memory_bytes: 256