http://acm.tongji.edu.cn/people/ps/showproblem.php?problem_id=1010
这道题显示超时。
Program TJU1010;
Var
  i, j, m, n, count: Longint;
  flag: Boolean;
Begin
  Writeln;
  Count := 0;
  Repeat
  Read(m,n);
  For i:=m To n Do
    Begin
      Flag := true;
      For j:=2 To round (sqrt(i)) Do
        If i Mod j = 0
          Then flag := false;
      If flag
        Then
          count := count + 1;
    End;
  If m=1 then count := count - 1;
  Writeln(count);
  count := 0;
  Until (n<0) Or (m<0)
End.