var a,b:text;
    n,nr,p,i:longint;
begin
assign(a,'fact.in');
reset(a);
assign(b,'fact.out');
rewrite(b);
read(a,n);p:=1;i:=1;
while nr<>n do begin
i:=i+1;
p:=p*i;
if p mod 10=0 then begin
while p mod 10=0 do begin
p:=p div 10;
nr:=nr+1;
end;
p:=p mod 10;
end;
if nr>n then begin write(b,'-1'); exit; end;
end;
write(b,i);
close(a);
close(b);
end.