C++ :

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<map>
using namespace std;
map<string,int> m;
typedef map<string,int>::iterator sit;
typedef pair<string,int> mypair;
string s;
sit it;
int w,n;
int main(){
//	ios::sync_with_stdio(false);	
	int i,x;
	cin>>w>>n;
	getchar();
	for(i=1;i<=w;++i)
	{
	  getline(cin,s);
	  m.insert(  mypair (s,i));
    }
    for(i=1;i<=n;++i){
    	scanf("%d",&x);
    	getchar();
    	getline(cin,s);
    	it=m.lower_bound(s);
    	if (it==m.end() || it->first.substr(0,s.size())!=s) cout<<-1<<endl; 
    	else{
    		bool flag=false;
    		x--;
    		while(x--)	
			  {
			      it++;
			      if (it==m.end()) 
				   {
				    cout<<-1<<endl;
				    flag=true;
				    break;
				   }
		      }
		    if (flag)continue;
    		if (it->first.substr(0,s.size())==s)
			{ cout<<it->second<<endl;}
    		else cout<<-1<<endl;
    	}
    }
}

Pascal :

var
  a:array[0..35005] of ansistring;
  b:array[0..35005] of longint;
  n,m:longint;
procedure init;
var i,j,t:longint;
    t1:ansistring;
begin
 readln(n,m);
 for i:=1 to n do
   begin
    readln(a[i]);
	b[i]:=i;
   end;
end;

procedure qsort(ll,rr:longint);
var i,j,t:longint;
    t1,x:ansistring;
begin
   i:=ll;j:=rr;x:=a[(ll+rr)>>1];
   repeat
     while a[i]<x do inc(i);
	 while a[j]>x do dec(j);
	 if i<=j then 
	   begin
	     t1:=a[i];a[i]:=a[j];a[j]:=t1;
		 t:=b[i];b[i]:=b[j];b[j]:=t;
		 inc(i);dec(j);
	   end;
   until i>j;
   
   if ll<j then qsort(ll,j);
   if i<rr then qsort(i,rr);   
end;

function find(ll,rr:longint;tt:ansistring):longint;
var mid:longint;
begin
  if ll=rr then exit(ll);
  if ll=rr-1 then 
    begin
	  if a[ll]>=tt then  exit(ll);
      exit(rr);	  
	end;
  mid:=(ll+rr)>>1;
  if a[mid]>=tt then exit(find(ll,mid,tt))
                else exit(find(mid+1,rr,tt));
end;

procedure main;
var i,j,x,yy:longint;
   tt:ansistring;
   ww:char;

begin
    qsort(1,n);
   for i:=1 to m do
     begin
	    read(x);
		read(ww);
		readln(tt);
		yy:=find(1,n,tt);
		if pos(tt,a[yy])=1 then
		                   begin
						     yy:=yy+x-1;
							 if pos(tt,a[yy])=1 then writeln(b[yy])
							                    else writeln(-1);
						   end
						   else 
						   begin
						    writeln(-1);
						   continue;
						   end;
	 end;
end;

begin
  init;main;
end.