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 be given.
Apply unknownprop_d26df5fbd1232d69dce26e2d7ea1db72a097f7918e729051f5e26168a38b9ff6 with
e707a.. x0 x1 x2 x3,
x0,
x1,
x2,
x3.
Let x4 of type ι → ι → ο be given.
The subproof is completed by applying H0.