contract DoubleStore =
  type state = {x1 : int | x1 >= 0} * {x2 : int | x2 >= 0}


  stateful entrypoint withdraw(amount : int) =
    require(amount > 0 && amount =< Contract.balance, "INVALID_AMOUNT")
    let (s1, s2) = state
    if(amount =< s1 && Call.caller == ak_2nqfyixM9K5oKApAroETHEV4rxTTCAhAJvjYcUV3PF1326LUsx)
      put((s1 - amount, s2))
      Chain.spend(Call.caller, amount)
    elif(amount =< s1 && Call.caller == ak_2CvLDbcJaw3CkyderTCgahzb6LpibPYgeodmCGcje8WuV5kiXR)
      put((s1, s2 - amount))
      Chain.spend(Call.caller, amount)
    else
      abort("INVALID_WITHDRAW")