How to write a binary tree expression in pure lambda calculus?

I have checked a lot of study materials, and they all only have example of list implementation in pure lambda calculus, which is

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Based on this, anyone can help me for implementing a binary tree( sort of nested list?) using pure lambda calculus( node and leaf, leaf comes with int number - eg. node(node(leaf(3),leaf(4))) ) ?

list = d.c.f.fi f2.x) list = d.c.f.fi f2.x)