import java.util.*;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String str1 = sc.nextLine();
String str2 = sc.nextLine();
int m = str1.length();
int n = str2.length();
char[] ch1 = str1.toCharArray();
char[] ch2 = str2.toCharArray();
int[][] dp = new int[m + 1][n + 1];
for(int i = 0; i <= m; i++) {
dp[i][0] = 0;
}
for(int j = 0; j <= n; j++) {
dp[0][j] = 0;
}
//二维dp数组,动态规划
int max = 0;
int index = 0;
for(int i = 1; i <= m; i++) {
for(int j = 1; j <= n; j++) {
if(ch1[i - 1] == ch2[j - 1]) {
dp[i][j] = dp[i - 1][j - 1] + 1;
}else {
dp[i][j] = 0;
}
if(dp[i][j] > max) {
index = i;
max = dp[i][j];
}
}
}
if(max == 0) {
System.out.println(-1);
}else {
String res = str1.substring(index - max, index);
System.out.println(res);
}
}
}