program fact;
var n2,n5,nn,i,p,n,aux:longint;
    fin,fout:text;
{*---------MAIN-----------------*}
begin
  assign(fin,'fact.in');
  assign(fout,'fact.out');
  reset(fin);
  rewrite(fout);
  readln(fin,p);
  n:=0;
  if p > 9 then
    begin
      aux:=p div 10;
      n:=5;
      for i:=1 to aux do
        n:=n+40;
    end;
  if p mod 10 > 0 then for i:=1 to p mod 10  do
                          n:=n+5;

  writeln(fout,n-1);
  close(fout);
end.