var f,g:text;
    n,k,nr,p:longint;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
if p>=10 then begin
k:=p div 5-1;
n:=p*5-k*5;
end
        else n:=p*5;
writeln(g,n);

close(f);
close(g);
end.