import std.stdio,std.math,std.string,std.conv,std.typecons,std.format;
import std.algorithm,std.range,std.array;

T[] readarr(T=long)(){return readln.chomp.split.to!(T[]);}
void scan(T...)(ref T args){auto input=readln.chomp.split;foreach(i,t;T)args[i]=input[i].to!t;}

//END OF TEMPLATE

void main(){
    long n,k;
    scan(n,k);
    min(n%k,abs(n%k-k)).writeln;
}
