const lim=2000000;
var n,i,j,nr:longint;
    a:array[1..lim]of byte;
    f,g:text;
begin
assign(f,'ciur.in'); reset(f);
assign(f,'ciur.out');rewrite(g);
read(f,n);
for i:=2 to lim do
if a[i]=0 then
begin
j:=i;
while j<n do
begin
j:=j+i;
a[i]:=1;
end;
end;
nr:=0;
for i:=1 to n do
if a[i]=0 then nr:=nr+1;
write(g,nr);
close(f);
close(g);
end.