program prog3;

var a:array[1..1000000] of longint;
j,k,n,i:longint;
  r:longint;
begin
readln(n);
for i:=1 to n do a[i]:=i;
a[1]:=0;
k:=1;
while (k<n div 2) do
begin
while (a[k]=0) do k:=k+1;
i:=k;
while (i<=n-k) do begin
i:=i+ k;
a[i]:=0;
end;
k:=k+1;
end;
r:=0;
for k:=1 to n do
if a[k]<>0 then begin r:=r+1;
end;
writeln(r);
end.