var c,p,n,i,min:longint;
    f,g:text;
    ok:boolean;
begin
assign(f,'fact.in');
assign(g,'fact.out');
reset(f);
rewrite(g);
readln(f,p);
c:=p div 6;
n:=5*(p-c);
writeln(g,n);
close(f);
close(g);
end.