var
n,m,i,j,count:longint;
teach:array [1..15000] of int64;
stud:array[1..1000000] of int64;

begin
  readln(n);
  for i:=1 to n do
  begin
    readln(teach[i]);
  end;
  readln(m);
  for i:=1 to m do
  begin
    readln(stud[i]);
     if (stud[i]>=teach[1]) and (stud[i]<=teach[n]) then
     begin
      for j:=1 to n do
      begin
        if stud[i]=teach[j] then
        begin
          count:=count+1;
          break;
        end;
        if stud[i]<teach[j] then
          break;
      end;
     end;
  end;
  writeln(count);
end.
Please tell me how to prevent time limit exceeded

Use binary search