Intervals (1) P51126

Write a program that, given two intervals, computes the interval corresponding to their intersection, or tells that it is empty.

Input

Input consists of four integer numbers $a_1$, $b_1$, $a_2$, $b_2$ that represent the intervals $[a_1,b_1]$ and $[a_2,b_2]$. Assume $a_1\le b_1$ and $a_2\le b_2$.

Output

Print “[]” if their intersection is empty, or “[$x$,$y$]” if this is their non-empty intersection.