program factorial;
var k,n,z:longint;
    f,t:text;

function fact(n,k,z:longint):int64;
var x,t:int64;
    i:longint;
    da:boolean;
    pb:boolean;
begin
  t:=n*n+100000;
  repeat
  da:=false;
  pb:=false;
  for i:=1 to t do
    begin
      if i>z then
        begin
          if i mod 5=0 then k:=k+1;
          if i mod 25=0 then
            begin
              z:=i;
              n:=n-1;
              pb:=true;
              break;
            end;
          if n+1=k then
            begin
              x:=i;
              da:=true;
             break;
            end;
        end
    end;
  until pb=false;
  if da then
           fact:=x
        else
           fact:=-1;
end;

begin
  assign(f,'fact.in');
  reset(f);
  read(f,k);
  close(f);
  n:=1;z:=0;
  {------------------}
  if k=0 then k:=1
         else k:=fact(k,n,z);
  {------------------}
  assign(t,'fact.out');
  rewrite(t);
  write(t,k);
  close(t);
end.