Var a, i, s, max: integer;

Begin

s := 1;

for i := 1 to 4 do begin

read(a);

if (a>max) then max := a;

end;

while (max > 0) do begin

if (max mod 10 mod 2 = 0) then s := s * max mod 10;

max := max div 10;

end;

writeln(s);

End.