var n,k,p:int64; f:text;

procedure ciur;
var i,j:longint;
begin
 p:=-1; k:=0;
 for i:=1 to n do
  if i-6<>p then inc(k) else p:=i;
end;

begin
 assign(f,'fact.in');
 reset(f);
 readln(f,n);
 close(f);
 ciur;
 assign(f,'fact.out');
 rewrite(f);
 if p=n then writeln(f,'-1') else writeln(f,k*5);
 close(f);
end.