want := new(Int).expSlow(x, y, m)
		if out.Cmp(want) != 0 {
			t.Errorf("x = %#x\ny=%#x\nz=%#x\nout=%#x\nwant=%#x\ndc: 16o 16i %X %X %X |p", x, y, m, out, want, x, y, m)
		}
	})
}

func BenchmarkExp3Power(b *testing.B) {
	const x = 3
	for _, y := range []Word{
		0x10, 0x40, 0x100, 0x400, 0x1000, 0x4000, 0x10000, 0x40000, 0x100000, 0x400000,
	} {
		b.Run(fmt.Sprintf("%#x", y), func(b *testing.B) {
			var z nat