求大佬指点！为啥我这个只能通过百分之80的样例，找不到错误了

	#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <set>
#include <map>
#include <vector>
#include <queue>
#include <string>
#include <bitset>
#include <utility>
#include <functional>
#include <iomanip>
#include <sstream>
#include <ctime>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>



	#define ll long long
#define ull unsigned long long



	using namespace std;



	const int MAXN=100;
const int MOD=1e9+7;



	ll p[10000];



	int main()
{



	    ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    int n,m;
    cin>>n>>m;
    for(int i=0;i<n;i++)
    {
        cin>>p[i];
    }
    sort(p,p+n);
    for(int i=0;i<m;i++)
    {
        ll u,v;
        cin>>u>>v;
        int flagk=0,t=0;
        for(int j=0;j<n;j++)
        {
            string q=to_string(p[j]);
            string w=to_string(v);
            int flag=0;
            if(q.length()<w.length()) flag=1;
            for(int k=q.length()-1,f2=w.length()-1;k>=q.length()-u;k--,f2--)
            {
                if(flag==1) break;
                if(w[f2]!=q[k])
                {
                    flag=1;
                    break;
                }
            }
            if(!flag)
            {
                flagk=1;
                t=j;
                break;
            }
        }
        if(flagk)
        {
            cout<<p[t]<<endl;
        }
        else cout<<-1<<endl;
    }
    return 0;
}