number of ways evaluation of expression such that value not changed one example:

How many ways we can do possible value-preserving parenthesis the following expression in such a way that value not changed after parenthesis with one constraint that parenthesis among one variable is not correct (i.e: $(i)+j+k$ is not acceptable) ?

as an example for expression $i+j+k$, parenthesis like $i+(j+k)$, $((i+j)+k)$ are correct parenthesis but $(i)+j+k$ is not. I take a complete short example as follows.
What's wrong with (i) + j + k ?

I live in a world where floating-point arithmetic has rounding errors, and where integer arithmetic has overflow checks, so (i + j) + k and i + (j + k) are most definitely not the same, for example if i is a large positive integer, and j, k are two large negative integers then the second one can produce an overflow (crash) while the first one doesn't.