var f,g:text;
  k,p,n,m:longint;
begin
  assign(f,'fact.in');
  reset(f);
  readln(f,p);
  close(f);
  k:=0;
  n:=1;
  repeat
    n:=n+1;
    m:=n;
    while m mod 5=0 do
       begin
       m:=m div 5;
       k:=k+1;
       end;
  until k=p;
assign(g,'fact.out');
rewrite(g);
writeln(g,n);
close(g);
end.