in input we have first array sorted an second unsorted

my solution needs to sort second array
so it has O(n*log n) quick sort.
where n is M(number of Student's dates)

then i solve problem in O(n):
--------------------------------
  While (j<=M) and (i<=N) do begin
    While S[j]<T[i] do inc(j);
    if S[j]=T[i] then begin
      inc(j);
      inc(Am);
    end else inc(i);
  end;
-----------------------------------
S-Array of teacher records
T-Array of student records
Am-number of complying dates

so, this algo is O(N*log n);