program infoarena5;
var f,g:text;
    n,contor,i,j:longint;
    v:array[1..2000000] of byte;
begin
        assign(f,'ciur.in'); reset(f);
        assign(g,'ciur.out'); rewrite(g);
        readln(f,n); contor:=0;
        for i:=2 to trunc(sqrt(n)) do
                for j:=2 to trunc(n/i) do
                        v[i*j]:=1;
        for i:=2 to n do
                if v[i] = 0 then
                   inc(contor);
        writeln(g,contor);
        close(f); close(g);
end.