program fcto;
var f:text;
    n,d,nr,p:longint;
begin
  assign(f,'fact.in');
  reset(f);
  readln(f,p);
  close(f);
  assign(f,'fact.out');
  rewrite(f);
  n:=5*(p+1);
  repeat
    d:=5;
    nr:=0;
    while n div d>0 do
      begin
        nr:=nr+n div d;
        d:=d*5
      end;
      n:=n-1;
   until nr<p;
     repeat
     n:=n+1;
    d:=5;
    nr:=0;
    while n div d>0 do
      begin
        nr:=nr+n div d;
        d:=d*5
      end;
   until nr>=p;
  write(f,n);
  close(f);
end.