{factorial}
var aux,p,i,e5,zerouri:0..100000000;
    f:text;
begin
e5:=0;
assign(f,'fact.in');
reset(f);
read(f,p);
close (f);
assign(f,'fact.out');
rewrite(f);
if p=0 then begin write(f,'1'); close (f); halt; end;
i:=0;
while zerouri<p do
begin
i:=i+5;
aux:=i;
while aux mod 5=0 do
      begin
      aux:=aux div 5;
      e5:=e5+1;
      end;
zerouri:=e5;
end;

if zerouri>p then
write (f,-1)
else
write (f,i);
close (f);
end.