program factoriale;
var n,i,fa,fc:integer;
    f,g:text;
begin
assign(f,'factoriale.in');
reset(f);
assign(g,'factoriale.out');
rewrite(g);
read(f,fc);
if fc<5 then write(g,fc*5)
        else begin
fa:=0;
n:=5*fc;
if n mod 25<>0 then begin
repeat
fa:=fa+ n div 5;
n:=n div 5;
until n=0;
if fc<>fa then
n:=(5*fc)-((fa-fc)*5)+5 mn;
          else n:=5*fc;
end;
write(g,n);
end;
if fc=0 then write(g,1);
close(f);
close(g);
end.