Program ciur;
var a:array[1..2000000] of boolean;
    i,j:longint;
    n,t:int64;
    f,q:text;
begin
assign(f,'ciur.in');
reset(f);
assign(q,'ciur.out');
rewrite(q);
readln(f,n);
for i:=1 to n do a[i]:=true;
t:=n-1;
        for i:=2 to n div 2 do
        begin
            if a[i]=true then
            begin
                j:=i*2;
                 while j<=n do
                  begin
                      if a[j]=true then begin t:=t-1; a[j]:=false; end;
                      j:=j+i;
                  end;
            end;
        end;
writeln(q,t);
close(f);
close(q);
end.