var nr,n,p,i,nn:longint;
f:text;
begin
assign(f,'fact.in');reset(f);
readln(f,p);
close(f);
assign(f,'fact.out');rewrite(f);
n:=4; nr:=0;
if n=0 then write(f,1)
else
while nr<>p do
      begin
      if nr>p then
              begin
              writeln(f,-1);
              break;
              end;
      inc(n);
      if n mod 5=0 then
         begin
              nn:=n;
              while nn mod 5=0 do
                    begin
                    inc(nr);
                    nn:=nn div 5;
                    end;
         end;
      end;
writeln(f,n);
close(f);
end.