
import java.util.*;

class Main {
    
	
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long N = sc.nextLong();
        long K = sc.nextLong();
        long ans = 0;
        ans = Math.min(K - N % K, N % K);
        
        
        System.out.println(ans);

	}

	
}
		
	 import java.util.*; util.* java class Main {
    
	
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long N = sc.nextLong();
        long K = sc.nextLong();
        long ans = 0;
        ans = Math.min(K - N % K, N % K);
        
        
        System.out.println(ans);

	}

	
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long N = sc.nextLong();
        long K = sc.nextLong();
        long ans = 0;
        ans = Math.min(K - N % K, N % K);
        
        
        System.out.println(ans);

	} main {
        Scanner sc = new Scanner(System.in);
        long N = sc.nextLong();
        long K = sc.nextLong();
        long ans = 0;
        ans = Math.min(K - N % K, N % K);
        
        
        System.out.println(ans);

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long N = sc.nextLong(); N sc.nextLong() sc.nextLong sc long K = sc.nextLong(); K sc.nextLong() sc.nextLong sc long ans = 0; ans 0 ans = Math.min(K - N % K, N % K) ans Math.min(K - N % K, N % K) Math.min Math K - N % K K N % K N K N % K N K System.out.println(ans) System.out.println System.out System System.out ans String[] args args

import java.util.*;

class Main {
    
	
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long N = sc.nextLong();
        long K = sc.nextLong();
        long ans = 0;
        ans = Math.min(K - N % K, N % K);
        
        
        System.out.println(ans);

	}

	
}
		
	
