{factorial}
uses crt;
var aux,p,i,e2,e5,zerouri:0..100000000;
    f,o:text;
begin
e2:=0;
e5:=0;
clrscr;
assign(f,'fact.in');
assign(o,'fact.out');
reset(f);
rewrite(o);
read(f,p);
if p=0 then begin write(o,'1'); close (o); halt; end;
i:=1;
repeat
i:=i+1;
aux:=i;
while aux mod 2=0 do
      begin
      aux:=aux div 2;
      e2:=e2+1;
      end;
while aux mod 5=0 do
      begin
      aux:=aux div 5;
      e5:=e5+1;
      end;
if e2>e5 then zerouri:=e5
         else zerouri:=e2;
until (zerouri=p) or (zerouri>p);
if zerouri>p then
write (o,-1)
else
write (o,i);
close (o);
close (f);
end.