var f,g:text;
    n,k,nr,p:longint;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
n:=p*5;
k:=5;
nr:=0;
while n mod k=0 do begin
      k:=k*5;
      inc(nr);
      end;
p:=p-nr+1;
n:=p*5;
write(g,n);
close(f);
close(g);
end.