Let x0 of type ο be given.
Let x1 of type ο be given.
Let x2 of type ο be given.
Let x3 of type ο be given.
Let x4 of type ο be given.
Assume H0: x0.
Apply orIL with
or (or (or x0 x1) x2) x3,
x4.
Apply or4I1 with
x0,
x1,
x2,
x3.
The subproof is completed by applying H0.