Return the index of the first occurrence of x or y in a string, or return -1 if the string does not contain an x or y. Hint: String objects have an indexOf() method that returns the first occurrence of one string within another, or -1 if the string can't be found. For example, if str is "mississippi", then str.indexOf("m") returns 0, str.indexOf("s") returns 2, and str.indexOf("q") returns -1.