program multiple;
{uses crt; }
var a,nr,b,r,i,j,n:integer;
    k:boolean;
    f,g:text;
    ciur:array[1..2000000]of byte;
begin
     {clrscr;}
     assign(f,'ciur.in');
     assign(g,'ciur.out');
     reset(f);
     rewrite(g);
     nr:=0;
     read(f,n);
     if(n=0) then write(g,0)
     else if((n=1)or(n=2)) then write(g,1)
     else
     begin
     fillchar(ciur,sizeof(ciur),1);
     for i:=2 to (n div 2) do
         for j:=2 to (n div i) do
             ciur[i*j]:=0;
     for i:=3 to n do
         if(ciur[i]=1) then inc(nr);
     write(g,nr+1);
     end;
     close(f);
     close(g);
     {readkey;}
end.