var f,g:text;
    p,i,x,p0:longint;
    ok:boolean;
begin
assign(f,'factorial.in');reset(f);
assign(g,'factorial.out');rewrite(g);
readln(f,p);
if p=0 then writeln(g,0)else if p<10
then writeln(g,p*5)
else writeln(g,(p-1)*5);
close(G);
end.