public static void main(String[] args) throws IOException {

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

String[] str11 = br.readLine().trim().split(" ");

String str1 = str11[0];

String str2 = str11[1];

System.out.println(Main1.getCommonStrLength(str1,str2));

}

public static String getCommonStrLength(String str1, String str2){

if(str1 == null || str2 == null){

return null;

}

if (str1.equals("") || str2.equals("")){

return null;

}

String max = "";

String min = "";

if(str1.length() < str2.length()){

max = str2;

min = str1;

} else {

max = str1;

min = str2;

}

String current = "";

for(int i = 0; i < min.length(); i++){

for(int begin = 0, end = min.length(); end <= min.length(); begin++,end++){

current = min.substring(begin, end);

if(max.contains(current)){

return current;

}

}

}

return null;

}

}