program ciur;
{$APPTYPE CONSOLE}
uses
  SysUtils;

var c,i,j,n,m:Longint;
    fin,fout:text;
    v:array [2..2000000] of byte;
{*-----------MAIN-------------*}
begin
        assign(fin,'ciur.in'); reset(fin);
        assign(fout,'ciur.out'); rewrite(fout);
        readln(fin,n); c:=0;
        //for i:=2 to n do v[i]:=0; //v[n+1]:=1;
        for i:=2 to n do
        begin
                if v[i] = 0 then
                begin
                        inc(c);
                        j:=i+i;
                        While j <= n do
                        begin
                                v[j]:=1;
                                inc(j,i);
                        end;
                end;
        end;

        writeln(fout,c);

        close(fin);
        close(fout);
end.