import java.util.HashSet;

import java.util.Scanner;

import java.util.Set;

public class Test1 {

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int N = in.nextInt();

int isPresent[] = new int[26];

for(int i = 0; i < 26; i++) isPresent[i] = 0;

for(int i = 0; i < N; i++) {

String s = in.next();

Set<Character> set = new HashSet<Character>();

for(int j = 0; j < s.length(); j++) {

set.add(s.charAt(j));

}

for(Character c: set) {

System.out.println(c);

isPresent[c - 'a']++;

}

}

int result = 0;

for(int i = 0; i < 26; i++) {

if(isPresent[i] == N) result++;

}

System.out.println(result);

in.close();

}

}