let n = readLine()!.split(separator: " ").map{Int($0)!}
var l = [Int]()
for _ in 1...n[0]{
    l += readLine()!.split(separator: " ").map{Int($0)!}
}
var c = 0
for (i,j) in l.sorted().enumerated(){
    if i % n[1] == 0 && i != 0{
        print()
    }
    print(j,terminator: " ")
}
print()