John has discovered various rocks. Each rock is composed of various elements, and each element is represented by a lower-case Latin letter from 'a' to 'z'. An element can be present multiple times in a rock. An element is called a gem-element if it occurs at least once in each of the rocks.
Given the list of rocks with their compositions, display the number of gem-elements that exist in those rocks.
The first line consists of an integer, , the number of rocks.
Each of the next lines contains a rock's composition. Each composition consists of lower-case letters of English alphabet.
Each composition consists of only lower-case Latin letters ('a'-'z'). length of each composition
Print the number of gem-elements that are common in these rocks. If there are none, print 0.
Only "a" and "b" are the two kinds of gem-elements, since these are the only characters that occur in every rock's composition.