BOJ_9252

#include<vector>
#include<algorithm>
#include<string>
#include<iostream>

using namespace std;
#pragma warning (disable : 4996)
template <typename type> type _max(type a, type b)
{
	return a > b ? a : b;
}
std::string str_a, str_b, str;
typedef struct {
	int x, y;
}POINT;
int ary[1111][1111] = { 0, };
int LCS(int x, int y)
{
	if (x < 0 || y < 0)
		return 1;
	else if (ary[x][y] == 0)
		if (str_a[x] == str_b[y])
			return ary[x][y] = LCS(x-1,y-1)+1;
		else
			return ary[x][y] = _max<int>(LCS(x-1,y), LCS(x,y-1)) ;
	else
		return ary[x][y];
}
POINT LCS_BACK(std::string * str, int x, int y)
{
	int dx[] = { 0, -1 ,-1}, dy[] = { -1, 0 ,-1}, dd = -1;
	if (x < 0 || y < 0)
		return{ -1, -1 };
	for (int i = 0; i < 2; i++)
		if (ary[x][y] == ary[x + dx[i]][y + dy[i]])
			dd = i;
	if (dd == -1)
	{
		*str += str_a[x];
		dd = 2;
	}
	return{ x + dx[dd], y + dy[dd]};
}
int main(int argc, char * argv[])
{
	std::cin >> str_a >> str_b;
	for (int i = 0; i < str_a.size(); i++)
		for (int j = 0; j < str_b.size(); j++)
			LCS(i, j);
	std::cout << ary[str_a.size() - 1][str_b.size() - 1] - 1 << endl;
	POINT p = {str_a.size()-1, str_b.size()-1};
	while ((p = LCS_BACK(&str, p.x , p.y )).x +  1);
	std::reverse(str.begin(), str.end());
	std::cout << str;
	return 0;
}