package sprint8.fin.A

fun main() {
    Node().apply {
        repeat(readln().toInt()) {
            readln() unpackTo this
        }
    }
        .prefix
        .let(::println)
}

infix fun String.unpackTo(root: Node): Node {
    var curNode = root
    var i = 0
    while (i < length && !this[i].isDigit()) {
        curNode = curNode.addVertex(this[i])
        if (curNode.vertices.size > 1) return curNode
        ++i
    }
    if (i == length) return curNode
    val repeatCount = this[i].digitToInt()
    i += 2
    val start = i
    var openedBraces = 1
    while (openedBraces > 0) {
        when (this[i]) {
            '[' -> ++openedBraces
            ']' -> --openedBraces
        }
        ++i
    }
    repeat(repeatCount) {
        curNode = substring(start until i - 1) unpackTo curNode
    }
    curNode = substring(i) unpackTo curNode
    return curNode
}

class Node {
    private val _vertices = mutableListOf<Vertex>()
    val vertices: List<Vertex>
        get() = _vertices

    fun addVertex(char: Char): Node =
        (vertices.firstOrNull { it.char == char } ?: Vertex(char).also { _vertices.add(it) }).destination

    val prefix
        get(): String =
            if (vertices.size == 1)
                vertices.first().let { "${it.char}${it.destination.prefix}" }
            else ""

    override fun toString() = prefix
}

data class Vertex(val char: Char, val destination: Node) {
    constructor(char: Char) : this(char, Node())
}