program asfsdf;
var f,g:text;
n,numar,nr,c:longint;
bifat:array[1..2000000] of integer;
begin
assign(f,'ciur.in'); reset(f);
assign(g,'ciur.out'); rewrite(g);
read(f,n);
   numar:=2;
     while numar<=n do
       begin
       nr:=numar;
          while nr<=n do
             begin
             bifat[nr]:=1;
             nr:=numar+nr;
             end;
       while bifat[numar]=1 do
         numar:=numar+1;
         c:=c+1;
       end;
       write(g,c);
close(f);
close(g);
end.