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_9f15ed4c4d5657c382f5b62b306ee6a0b8989ef4de6807aa67a5d58547b70eee 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.