#include<iostream>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
using namespace std;
int n,q,a[10000001],x,y;
int pd(int x,int y)
{
	int i,z=10,minn=0x7fffffff,f=0;
	for(i=2;i<=x;i++)
		z*=10;
	for(i=1;i<=n;i++)
		if(a[i]%z==y&&a[i]<minn)
		{
			f=1;
			minn=a[i];
		}
	if(f==0)
		return -1;
	return minn;
}
int main()
{
	int i;
	cin>>n>>q;
	for(i=1;i<=n;i++)
		cin>>a[i];
	for(i=1;i<=n;i++)
	{
		cin>>x>>y;
		cout<<pd(x,y)<<endl;
	}
	return 0;
}