searchBits = 7
			regionBits = 9
			regionMask = 1<<regionBits - 1
		)
		idx := n >> searchBits
		buf := fromM49[m49Index[idx]:m49Index[idx+1]]
		val := uint16(n) << regionBits // we rely on bits shifting out
		i := sort.Search(len(buf), func(i int) bool {
			return buf[i] >= val
		})
		if r := fromM49[int(m49Index[idx])+i]; r&^regionMask == val {
			return Region(r & regionMask), nil
		}
	}
	var e ValueError

	993, 994, 995, 996, 997, 998, 720, 887,
	175, 891, 710, 894, 180, 716, 999,
}

// m49Index gives indexes into fromM49 based on the three most significant bits
// of a 10-bit UN.M49 code. To search an UN.M49 code in fromM49, search in
//
//	fromM49[m49Index[msb39(code)]:m49Index[msb3(code)+1]]
//
// for an entry where the first 7 bits match the 7 lsb of the UN.M49 code.