Let

be an arbitrary nonempty set. For each

, let

be a scalar-valued function depending on a finite number of variables:
![$$
f_\gamma \in C([t_1, t_2] \times \mathbb{R}^{n_\gamma}), \quad f_\gamma = f_\gamma(t, x_{\sigma_1}, \dots, x_{\sigma_{n_\gamma}}),
$$ $$
f_\gamma \in C([t_1, t_2] \times \mathbb{R}^{n_\gamma}), \quad f_\gamma = f_\gamma(t, x_{\sigma_1}, \dots, x_{\sigma_{n_\gamma}}),
$$](https://dxdy-02.korotkov.co.uk/f/1/e/a/1ea953c92708648e19bf4f92b7c59e9d82.png)
where

is a finite subset of indices, and
![$$
\sup_{[t_1, t_2] \times \mathbb{R}^{n_\gamma}} |f_\gamma| \le M_\gamma.
$$ $$
\sup_{[t_1, t_2] \times \mathbb{R}^{n_\gamma}} |f_\gamma| \le M_\gamma.
$$](https://dxdy-04.korotkov.co.uk/f/3/4/9/349ab9cf0f0968022df6c6ea20aac59982.png)
Theorem.
The Cauchy problem

has a solution

such that
![$x_\gamma \in C^1[t_1, t_2]$ $x_\gamma \in C^1[t_1, t_2]$](https://dxdy-04.korotkov.co.uk/f/3/5/2/352d84c8a3085898c91d00b06cd34c0582.png)
for each

.
What is your take on this construction?