PROGRAM POR1;
VAR  N,I,J,K:LONGINT;
      V:ARRAY[1..2000001]OF BOOLEAN;
BEGIN
      ASSIGN(F,'CIUR.IN');RESET(F);
      ASSIGN(G,'CIUR.OUT');REWRITE(G);
      READLN(F,N);
      FOR I:=2 TO N DO
       IF not (V[I]) THEN  begin
        K:=K+1;
          FOR J:=2 TO N DIV I DO
           V[I*J]:=true;
       END;
   WRITE(G,K);
      CLOSE(F);
      CLOSE(G);
END.