Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι be given.
Let x3 of type ι be given.
The subproof is completed by applying unknownprop_884f980f78373fe666c53ffbb6640e20eddad6ad5ffb6e2dff45a96d66854b70 with
4,
λ x4 . If_i (x4 = 0) x0 (If_i (x4 = 1) x1 (If_i (x4 = 2) x2 x3)).