Let x0 of type ι be given.
Let x1 of type ι → ι → ι be given.
Let x2 of type ι → ι → ι be given.
Let x3 of type ι → ι be given.
Apply unknownprop_939b397a6128ac053e8dbe8eb38159483eb0ba68b22e3a7577c8c19a39a160ed with
a255b.. x0 x1 x2 x3,
x0,
x1,
x2,
x3.
Let x4 of type ι → ι → ο be given.
The subproof is completed by applying H0.