Let $x_1, y_1, \dots, x_N, y_N \in \mathbb{R}$ each be a D993: Real number such that

(i)	\begin{equation} x_1 \leq y_1, \quad \dots, \quad x_N \leq y_N \end{equation}

Then \begin{equation} \sum_{n = 1}^N x_n \leq \sum_{n = 1}^N y_n \end{equation}