#include <bits/stdc++.h>

using namespace std;

const int INF = 1000000;

int dp[1201][1201][3][3];

int min(int a[3]) {
    return min(min(a[0], a[1]), a[2]);
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n, m;
    string s, t;
    cin >> n >> m >> s >> t;
    for (int i = 1; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            dp[0][0][i][j] = INF;
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < 3; j++) {
            dp[i][0][0][j] = INF;
            dp[i][0][1][j] = 9 + 2 * (i - 1);
            dp[i][0][2][j] = INF;
        }
    }
    for (int i = 1; i <= m; i++) {
        for (int j = 0; j < 3; j++) {
            dp[0][i][0][j] = INF;
            dp[0][i][1][j] = INF;
            dp[0][i][2][j] = 9 + 2 * (i - 1);
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            for (int k = 0; k < 3; k++) {
                int c_sub, c_ins, c_del;
                if (s[i - 1] == t[j - 1]) c_sub = 0;
                else c_sub = 5;
                if (k == 1) c_ins = 2;
                else c_ins = 9;
                if (k == 2) c_del = 2;
                else c_del = 9;
                dp[i][j][0][k] = min(INF, min(dp[i - 1][j - 1][k]) + c_sub);
                dp[i][j][1][k] = min(INF, min(dp[i - 1][j][k]) + c_ins);
                dp[i][j][2][k] = min(INF, min(dp[i][j - 1][k]) + c_del);
            }
        }
    }
    int cost = INF, now = 0;
    for (int i = 0; i < 3; i++) {
        int tmp = min(dp[n][m][i]);
        if (tmp < cost) {
            cost = tmp;
            now = i;
        }
    }
    int idx_s = n, idx_t = m;
    string ali_s = "", ali_t = "";
    while (idx_s > 0 || idx_t > 0) {
        int tmp;
        int past;
        switch(now) {
            case 0:
                ali_s = s[idx_s - 1] + ali_s;
                ali_t = t[idx_t - 1] + ali_t;
                idx_s--;
                idx_t--;
                tmp = (s[idx_s] == t[idx_t]?0:5);
                for (int i = 0; i <= 2; i++) {
                    if (dp[idx_s + 1][idx_t + 1][now][i] == min(dp[idx_s][idx_t][i]) + tmp) {
                        past = i;
                        break;
                    }
                }
                break;
            case 2:
                ali_s = "-" + ali_s;
                ali_t = t[idx_t - 1] + ali_t;
                idx_t--;
                for (int i = 0; i <= 2; i++) {
                    tmp = (now == i?2:9);
                    if (dp[idx_s][idx_t + 1][now][i] == min(dp[idx_s][idx_t][i]) + tmp) {
                        past = i;
                        break;
                    }
                }
                break;
            case 1:
                ali_s = s[idx_s - 1] + ali_s;
                ali_t = "-" + ali_t;
                idx_s--;
                for (int i = 0; i <= 2; i++) {
                    tmp = (now == i?2:9);
                    if (dp[idx_s][idx_t + 1][now][i] == min(dp[idx_s][idx_t][i]) + tmp) {
                        past = i;
                        break;
                    }
                }
                break;
        }
        now = past;
    }
    cout << cost << "\n";
    cout << ali_s << "\n";
    cout << ali_t << "\n";
    return 0;
}