var p,n,zero,j:longint;
var t:text;
begin
zero:=0;
n:=0;
assign(t,'fact.in'); reset(t);
readln(t,p);
repeat
  begin
    n:=n+1;
    j:=n;
    while j mod 5 = 0 do
      begin
        zero:=zero+1;
        j:=j div 5;
      end;

  end;
until zero>=p;
close(t);
assign(t,'fact.out'); rewrite(t);
if zero=p then writeln(t,n)
  else writeln(t,'-1');
close(t);
end.