[Build]

(Keeper, keeper, keeper, keeper)

(Keeper, keeper, keeper, keep)

(Keeper, keeper, keeper, keeper)

(Keeper, keeper, keep)

[Drop]

[Build]

(Keeper, keeper, keeper, keeper)

(Keeper, keeper, keeper, keep)

(Keeper, keeper, keeper, keeper)

(Keeper, keeper, keep)

[Drop]

(Keep)

(Keep)