program factoriale;
var n,i,fa,fc,j,k:integer;
    f,g:text;
begin
assign(f,'factoriale.in');
reset(f);
assign(g,'factoriale.out');
rewrite(g);
read(f,fc);
if ((fc<5)and(fc<>0)) then write(g,fc*5)
                      else begin
fa:=0;
n:=5*fc;
repeat
fa:=fa+ n div 5;
n:=n div 5;
until n=0;
n:=5*fc;
while fc<fa do begin
k:=n;
j:=0;
while k mod 5=0 do begin
k:=k div 5;
inc(j);
end;
fa:=fa-j;
n:=n-5;
end;
write(g,n);
end;
if fc=0 then write(g,1);
close(f);
close(g);
end.