using EducationalDPContest.Questions;
using EducationalDPContest.Extensions;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace EducationalDPContest.Questions
{
    public class QuestionF : AtCoderQuestionBase
    {
        public override IEnumerable<object> Solve(TextReader inputStream)
        {
            var s = inputStream.ReadLine();
            var t = inputStream.ReadLine();

            var dpLongest = new int[s.Length + 1, t.Length + 1];

            for (int i = 1; i <= s.Length; i++)
            {
                for (int j = 1; j <= t.Length; j++)
                {
                    if (s[i - 1] == t[j - 1])
                    {
                        UpdateWhenLarge(ref dpLongest[i, j], dpLongest[i - 1, j - 1] + 1);
                    }

                    UpdateWhenLarge(ref dpLongest[i, j], dpLongest[i - 1, j]);
                    UpdateWhenLarge(ref dpLongest[i, j], dpLongest[i, j - 1]);
                }
            }

            var result = new LinkedList<char>();

            int k = s.Length;
            int l = t.Length;

            while (k > 0 && l > 0)
            {
                if (dpLongest[k, l] == dpLongest[k - 1, l])
                {
                    k--;
                }
                else if (dpLongest[k, l] == dpLongest[k, l - 1])
                {
                    l--;
                }
                else
                {
                    k--;
                    l--;
                    result.AddFirst(s[k]);
                }
            }

            yield return string.Concat(result);
        }
    }
}


namespace EducationalDPContest
{
    class Program
    {
        static void Main(string[] args)
        {
            IAtCoderQuestion question = new QuestionF();    // 問題に合わせて書き換え
            var answers = question.Solve(Console.In);
            foreach (var answer in answers)
            {
                Console.WriteLine(answer);
            }
        }
    }
}

#region Base Classes

namespace EducationalDPContest.Questions
{

    public interface IAtCoderQuestion
    {
        IEnumerable<object> Solve(string input);
        IEnumerable<object> Solve(TextReader inputStream);
    }

    public abstract class AtCoderQuestionBase : IAtCoderQuestion
    {
        public IEnumerable<object> Solve(string input)
        {
            var stream = new MemoryStream(Encoding.Unicode.GetBytes(input));
            var reader = new StreamReader(stream, Encoding.Unicode);

            return Solve(reader);
        }

        public abstract IEnumerable<object> Solve(TextReader inputStream);

        protected void UpdateWhenSmall<T>(ref T value, T other) where T : IComparable<T>
        {
            if (other.CompareTo(value) < 0)
            {
                value = other;
            }
        }

        protected void UpdateWhenLarge<T>(ref T value, T other) where T : IComparable<T>
        {
            if (other.CompareTo(value) > 0)
            {
                value = other;
            }
        }
    }

}

#endregion

#region Collections

namespace EducationalDPContest.Collections
{
    public static class SearchExtension
    {
        public static int GetGreaterEqualIndex<T>(this T[] span, T minValue) where T : IComparable<T>
        {
            int ng = -1;
            int ok = span.Length;

            return BoundaryBinarySearch(span, v => v.CompareTo(minValue) >= 0, ng, ok);
        }

        public static int GetSmallerEqualIndex<T>(this T[] span, T maxValue) where T : IComparable<T>
        {
            int ng = span.Length;
            int ok = -1;

            return BoundaryBinarySearch(span, v => v.CompareTo(maxValue) <= 0, ng, ok);
        }

        private static int BoundaryBinarySearch<T>(T[] span, Predicate<T> predicate, int ng, int ok)
        {
            // めぐる式二分探索
            // Span.BinarySearchだとできそうでできない（lower_boundがダメ）
            while (Math.Abs(ok - ng) > 1)
            {
                int mid = (ok + ng) / 2;

                if (predicate(span[mid]))
                {
                    ok = mid;
                }
                else
                {
                    ng = mid;
                }
            }
            return ok;
        }
    }
}

#endregion
#region Extensions

namespace EducationalDPContest.Extensions
{
    internal static class TextReaderExtensions
    {
        internal static int ReadInt(this TextReader reader) => int.Parse(ReadString(reader));
        internal static long ReadLong(this TextReader reader) => long.Parse(ReadString(reader));
        internal static double ReadDouble(this TextReader reader) => double.Parse(ReadString(reader));
        internal static string ReadString(this TextReader reader) => reader.ReadLine();

        internal static int[] ReadIntArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(int.Parse).ToArray();
        internal static long[] ReadLongArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(long.Parse).ToArray();
        internal static double[] ReadDoubleArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(double.Parse).ToArray();
        internal static string[] ReadStringArray(this TextReader reader, char separator = ' ') => reader.ReadLine().Split(separator);
    }
}

#endregion

Measured memory_bytes: 46304