#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int) a.size()
#define all(a) a.begin(),a.end()
#define vec(...) vector<__VA_ARGS__>
#define _4c5UlRw ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}

void slv(){
	int a,b;
	cin>>a>>b;
	int ho=0;
	if(b<0){
		b*=-1;
		ho=1;
	}
	if(a<0){
		ho^=1;
		a*=-1;
	}
	print(ho?b-(a%b):a%b);
}

signed main(){
_4c5UlRw;
	slv();
}