# Gemstones

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#
#   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 N rocks with their compositions, display the number of gem-elements that exist in those rocks.
#
#   Input Format
#   The first line consists of an integer N, the number of rocks.
#   Each of the next N lines contains a rock's composition.
#   Each composition consists of lower-case letters of English alphabet.
#
#   Constraints
#   1 <= N <= 100
#   Each composition consists of only lower-case Latin letters ('a'-'z').
#   1 <= length of each composition<= 100
#
#   Output Format
#   Print the number of gem-elements that are common in these rocks. If there are none, print 0.
#
#   Sample Input
#   3
#   abcdde
#   baccd
#   eeabg
#
#   Sample Output
#   2
#
#   Explanation
#   Only "a" and "b" are the two kinds of gem-elements,
#   since these are the only characters that occur in every rock's composition.
#
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