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+## Which Are In?
+
+Given two arrays of strings a1 and a2 return a sorted array r in lexicographical order of the strings of a1 which are substrings of strings of a2.
+
+**Example 1:**
+```
+a1 = ["arp", "live", "strong"]
+
+a2 = ["lively", "alive", "harp", "sharp", "armstrong"]
+
+returns ["arp", "live", "strong"]
+```
+**Example 2:**
+```
+a1 = ["tarp", "mice", "bull"]
+
+a2 = ["lively", "alive", "harp", "sharp", "armstrong"]
+
+returns []
+```
+**Notes:**
+
+Arrays are written in "general" notation. See "Your Test Cases" for examples in your language.
+In Shell bash a1 and a2 are strings. The return is a string where words are separated by commas.
+Beware: r must be without duplicates.