#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>


typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;







int main()
{

    int Q;
    Q = 1;
    //cin >> Q;

    while (Q--) {
        int n, m;
        cin >> n >> m;
        int ans = abs(m);
        for (int i = -1000; i <= 1000; i++) {
            int t = n - i * m;
            if (t>=0&&abs(m) > t && abs(t) < abs(ans))ans = t;
        }
        cout << ans << endl;

    }
    return 0;
}