package main import ( "bufio" "container/heap" "fmt" "os" "sort" "strconv" ) func out(x ...interface{}) { fmt.Println(x...) } var sc = bufio.NewScanner(os.Stdin) func getInt() int { sc.Scan() i, e := strconv.Atoi(sc.Text()) if e != nil { panic(e) } return i } func getInts(N int) []int { ret := make([]int, N) for i := 0; i < N; i++ { ret[i] = getInt() } return ret } func getString() string { sc.Scan() return sc.Text() } // min, max, asub, absなど基本関数 func max(a, b int) int { if a > b { return a } return b } func min(a, b int) int { if a < b { return a } return b } func asub(a, b int) int { if a > b { return a - b } return b - a } func abs(a int) int { if a >= 0 { return a } return -a } func lowerBound(a []int, x int) int { idx := sort.Search(len(a), func(i int) bool { return a[i] >= x }) return idx } func upperBound(a []int, x int) int { idx := sort.Search(len(a), func(i int) bool { return a[i] > x }) return idx } //--------------------------------------------- // priority queue //--------------------------------------------- type pqi struct{ a string } type priorityQueue []pqi func (pq priorityQueue) Len() int { return len(pq) } func (pq priorityQueue) Swap(i, j int) { pq[i], pq[j] = pq[j], pq[i] } func (pq priorityQueue) Less(i, j int) bool { return pq[i].a < pq[j].a } func (pq *priorityQueue) Push(x interface{}) { *pq = append(*pq, x.(pqi)) } func (pq *priorityQueue) Pop() interface{} { x := (*pq)[len(*pq)-1] *pq = (*pq)[0 : len(*pq)-1] return x } func main() { sc.Split(bufio.ScanWords) sc.Buffer([]byte{}, 1000000) N := getInt() pq := priorityQueue{} for i := 0; i < N; i++ { s := getString() heap.Push(&pq, pqi{s}) } ans := "" for len(pq) != 0 { s := heap.Pop(&pq).(pqi).a ans = ans + string(s[0]) s = s[1:] if len(s) != 0 { heap.Push(&pq, pqi{s}) } // out(pq) } out(ans) }