Program factorial;
VAR
  Be,Ki: Text;
  p,zero,n: Int64;

procedure feladat;
var aux:Int64;
begin
n:=0;
zero:=0;
aux:=0;
while zero<p do begin
if zero + 6 < p then begin
n:=n+25;
zero:=zero+6;
aux:=n div 25;
end
else begin
n:=n+5;
aux:=n;
end;
while aux mod 5 = 0 do begin
aux:=aux div 5;
inc(zero);
end;
end;
Write(Ki,n);
end;

BEGIN

Assign(Be,'fact.in'); Reset(Be);
Assign(Ki,'fact.out'); Rewrite(Ki);

Read(Be,p);
if p=0 then Write(Ki,1) else
feladat;
Close(Be); Close(Ki);

END.