program ciur;
{$APPTYPE CONSOLE}
uses
  SysUtils;

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

        c:=0;
        For i:=1 to n do if v[i] = 1 then inc(c);

        writeln(fout,c-1);

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