program fact;
var p,n,k,j:qword;
    u:boolean;
    f,g:text;
begin
  assign(f,'fact.in'); reset(f); readln(f,p);  close(F);
  assign(g,'fact.out'); rewrite(g);
  n:=0; k:=0;
  while k<=p do begin
     n:=n+5; j:=n;
     while (j mod 5=0) and (j<>0) do begin
                                     j:=j div 5;
                                     inc(k);
                                     end;
                  end;
  n:=n-5;

  if p=0 then write(g,1)
            else write(g,n);
  close(g);
end.