let pubA = PassthroughSubject<Int, Never>()
let pubB = PassthroughSubject<Int, Never>()
let pubC = PassthroughSubject<Int, Never>()
let pubD = PassthroughSubject<Int, Never>()

let cancellable = pubA
    .merge(with: pubB, pubC, pubD)
    .sink { print("\($0)", terminator: "/" )}

pubA.send(1)
pubB.send(40)
pubC.send(90)
pubD.send(-1)

pubA.send(2)
pubB.send(50)
pubC.send(100)
pubD.send(-2)