for A being free preIfWhileAlgebra
for I1, I2 being Element of A
for n being Nat st I1 \; I2 in (ElementaryInstructions A) |^ n holds
ex i being Nat st
( n = i + 1 & I1 in (ElementaryInstructions A) |^ i & I2 in (ElementaryInstructions A) |^ i )