program ciur;
const pas=[2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233];

var f,g:text;
t,k:integer; n,i,j:longint;
begin
assign(f,'ciur.in');reset(f);
assign(g,'ciur.out');rewrite(g);
read(f,n);
for i:=2 to n do begin
if i in pas then k:=k+1;
end;
write(g,k);
close(f);
close(g);
end.