var c:array[1..2000000] of byte;
    x,nr,i,k,n:longint;
    f:text;
begin
     assign(f,'ciur.in'); reset(f);
     readln(f,n);
     close(f);
     assign(f,'ciur.out'); rewrite(f);
     k:=3;
     while k<=trunc(sqrt(n)) do
     begin
          x:=k;
          while x<=n do
          begin
               c[x]:=1;
               x:=x+k;
          end;
          k:=k+2;
     end;  i:=1;      nr:=0;
     while i<=n do
     begin
          i:=i+2;
          if c[i]=0 then inc(nr);
     end;
     writeln(f,nr+1);
     close(f);
end.