const max5=10;
var p5:array[0..max5]of longint;
    p,i:integer;
    n:longint;

procedure crearep5;
var i:byte;
begin
p5[0]:=1;
for i:=1 to max5 do p5[i]:=p5[i-1]*5;
end;

{procedure verifica;
begin
p:=0;
for i:=1 to max5 do p:=p+n div p5[i];
writeln;
write(p);
end;}

begin
crearep5;
assign(input,'fact.in');
reset(input);
assign(output,'fact.out');
rewrite(output);
read(p);
n:=0;
while p>0 do
  begin
  n:=n+5;
  for i:=1 to max5 do if n mod p5[i]=0 then p:=p-1;
  end;
if p<0 then write('-1')
       else write(n);
{verifica;}
close(output);
close(input);
end.