{factorial}
uses crt;
var aux,p,i,e2,e5,zerouri:0..100000000;
    f:text;
begin
e2:=0;
e5:=0;
clrscr;
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:=1;
repeat
i:=i+1;
aux:=i;
while aux mod 5=0 do
      begin
      aux:=aux div 5;
      e5:=e5+1;
      end;
zerouri:=e5;
until (zerouri=p) or (zerouri>p);
if zerouri>p then
write (f,-1)
else
write (f,i);
close (f);
end.