#include<bits/stdc++.h>
#define int long long
#define double long double
#define lowbit(x) x&(-x)
#define fastios ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define endl '\n'
#define el puts("")
#define udm unordered_map<int,int>
#define set_0(a) memset(&a,0,sizeof(a))
#define set_unint(a) memset(&a,-1,sizeof(a))
using namespace std;
//define_var
const int M=2e5+9,inf=1e18;
int s1[30],s2[30],p[30];
//define_var
//function_begin
int read()
{
	int x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){if(c=='-') f=-1;c=getchar();}
	while(c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
	return x*f;
}
void write(int x)
{
	if(x<0) putchar('-'),x=-x;
	if(x>9) write(x/10);
	putchar(x%10+'0');
}
void pri()
{
	int ps=-1;
	for(int i=29;i>=0;i--)
	{
		if(s2[i])
		{
			ps=i;
			break;
		}
	}
	if(ps==-1)
	{
		if(p[0]<9)
		cout<<1<<endl;
		else
			cout<<-1<<endl;
		return;
	}
	for(int i=ps;i>=0;i--)
		cout<<s2[i];
	cout<<endl;
}
bool judge(int w,int k)
{
	memset(s2,0,sizeof(s2));
	for(int i=0;i<30;i++)
		s1[i]=p[i];
	int pos=0;
	for(int i=w;i<30;i++)
	{
		if(pos<k)
		{
			if(s1[i]==0)
				return false;
			s2[i]=max(0ll,10-s1[i]);
			s1[i+1]++;
			pos++;
		}
		else
		{
			s2[i]=0;
			if(s1[i]>=10)
				s1[i+1]++,pos++;
		}
	}
	if(pos==k)
		return true;
	return false;
}
//function_end
//solve_begin
void solve()
{
	int x,k;
	cin>>x>>k;
	memset(p,0,sizeof(p));
	for(int i=0;x;i++)
		p[i]=x%10,x/=10;
	for(int i=0;i<20;i++)
	{
		if(judge(i,k))
		{
			pri();
			return;
		}
	}
	cout<<-1<<endl;
}
//solve_end
//main_begin
signed main()
{
//	fastios
	int T=1;
	cin>>T;
	while(T--)
		solve();
}
//main_end