Program Eratostene;
var T:array[1..2000000] of 0..1;
    p,nr,i,j,n,x:longint;
    f1,f2:text;
begin
assign(f1,'ciur.in'); reset(f1);
assign(f2,'ciur.out'); rewrite(f2);
readln(f1,n);
p:=2;
for i:=p to n do
  if T[i]=0 then
             begin
              x:=i*i;
               while x<=n do
                begin
                 T[x]:=1;
                 inc(nr);
                 x:=x+i;
                end;
             end;
nr:=n-nr;
writeln(f2,nr);
close(f1); close(f2);
end.