const put=3;
      p:array[1..put] of longint=(5, 25, 125);

var i, j, n:longint;
    f, g:text;

function fact (x:longint):longint;
var t:integer;
  begin
  t:=0;
  for i := 1 to put do t:=t+(x div p[i]);
  fact:=t;
  end;

begin
assign (f, 'fact.in'); reset (f);
assign (g, 'fact.out'); rewrite (g);

readln (n);
while n <>0 do
  begin
  writeln (fact(n));
  readln (n);
  end;

close (f); close (g);
end.