program factorial;
const v:array[1..12] of longint=
      (5, 25, 125, 625, 3125, 15625, 390625, 1953125, 9765625, 9765625, 244140625, 1220703125);
var n,p:longint;
function f:longint;
var k,i:longint;
begin
 k:=0;
 for i:=1 to 12 do
  k:=k+trunc(n/v[i]);
 f:=k;
end;
begin
 assign(input,'fact.in');
 reset(input);
 readln(p);
 close(input);
 assign(output,'fact.out');
 rewrite(output);
 if p=0 then begin writeln(1); close(output); exit; end;
 n:=p*5;
 while f>p do dec(n,5);
 writeln(n);
 close(output);
end.