class Solution {
    private data class State(val result: Long, val n: Long) {
        fun update(
            target: Long,
            mask: Long,
        ): State =
            when {
                n > 0 && mask.and(target) == 0L -> State(result.or((n.and(1L)) * mask), n.shr(1))
                else -> this
            }
    }

    fun minEnd(
        n: Int,
        x: Int,
    ): Long =
        (0..Long.SIZE_BITS)
            .map { 1L.shl(it) }
            .fold(State(x.toLong(), n - 1L)) { s, mask ->
                s.update(x.toLong(), mask)
            }.result
}