import java.io.*;
public class longestCommonSubstring
{
private static String longestCommonSubstring(String S1, String S2)
{
int Start = 0;
int Max = 0;
for (int i = 0; i < S1.length(); i++)
{
for (int j = 0; j < S2.length(); j++)
{
int x = 0;
while (S1.charAt(i + x) == S2.charAt(j + x))
{
x++;
if (((i + x) >= S1.length()) || ((j + x) >= S2.length())) break;
}
if (x > Max)
{
Max = x;
Start = i;
}
}
}
return S1.substring(Start, (Start + Max));
}
public static void main(String args[])
{
readString.printSt(longestCommonSubstring(readString.getSt(),reverseString.reverseString(readString.getSt() )));
}
}