#include<bits/stdc++.h>

using namespace std;

const int INF = (int)1e9;

vector<vector<int>> dp;

string ans1 = "", ans2 = "";

int diff(char a, char b)
{
    if(a != b)
        return 1;
    else
        return 0;
}

int cnt, k = 0, k1 = 0;
string s1, s2;

void f(int i, int j)
{
    if(i > 0 && dp[i][j] == dp[i - 1][j] + 1)
    {
        ans1.push_back(s1[i - 1]);
        ans2.push_back('-');
        k1++;
        f(i - 1, j);
    }
    else if(i > 0 && j > 0 && (dp[i][j] == dp[i - 1][j - 1] + 1 || dp[i][j] == dp[i - 1][j - 1]))
    {
        ans1.push_back(s1[i - 1]);
        ans2.push_back(s2[j - 1]);
        f(i - 1, j - 1);
    }
    else if(j > 0 && dp[i][j] == dp[i][j - 1] + 1)
    {
        ans1.push_back('-');
        ans2.push_back(s2[j - 1]);
        f(i, j - 1);
    }

}

int DP(int i, int j)
{
    if(dp[i][j] == INF)
    {
        if(j == 0)
            return dp[i][j] = i;
        else if(i == 0)
            return dp[i][j] = j;
        else
        {
            int ins = DP(i, j - 1) + 1;
            int del = DP(i - 1, j) + 1;
            int sub = DP(i - 1, j - 1) + diff(s1[i - 1], s2[j - 1]);
            return dp[i][j] = min({ins, del, sub});
        }
    }
    else
        return dp[i][j];
}

main()
{
    cin >> s1 >> s2;
    int n = s1.size(), m = s2.size();
    dp.resize(n + 2, vector<int>(m + 2, INF));
    cnt = DP(n, m);
    f(n, m);
    int k2 = 0, k3 = 0;
    reverse(ans1.begin(), ans1.end());
    reverse(ans2.begin(), ans2.end());
    cout << cnt << "\n";
    cout << ans1 << "\n" << ans2 << "\n";
}