#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> PII;

const int MAXN = 1234;
int f[MAXN][MAXN][3];
const int INF = 1e9;

int n, m;
char s[MAXN], t[MAXN];
char p[MAXN * 2], q[MAXN * 2];

void solve(int casi) {
    scanf("%d%d", &n, &m);
    scanf("%s", s + 1);
    scanf("%s", t + 1);
    for (int i = 0; i <= n; ++i) {
        for (int j = 0; j <= m; ++j) {
            for (int k = 0; k < 3; ++k) {
                f[i][j][k] = INF;
            }
        }
    }
    f[0][0][0] = 0;
    // for (int j = 0; j < 3; ++j) f[0][0][j] = 0;
    for (int i = 0; i <= n; ++i) {
        for (int j = (i == 0); j <= m; ++j) {
            // s[i] && t[j]
            if (i > 0 && j > 0)
                f[i][j][0] = min({f[i - 1][j - 1][0], f[i - 1][j - 1][1], f[i - 1][j - 1][2]}) + (s[i] != t[j]) * 5;
            // s[i] && -
            if (i > 0)
                f[i][j][1] = min({f[i - 1][j][0] + 9, f[i - 1][j][1] + 2, f[i - 1][j][2] + 9});
            // - && t[j]
            if (j > 0)
                f[i][j][2] = min({f[i][j - 1][0] + 9, f[i][j - 1][1] + 9, f[i][j - 1][2] + 2});
        }
    }
    int ans = min({f[n][m][0], f[n][m][1], f[n][m][2]});
    int i = n, j = m, k = (ans == f[n][m][0]) ? 0 : (ans == f[n][m][1] ? 1 : 2), l = 0;
    while (i > 0 || j > 0) {
        if (k == 0) {
            int o = f[i][j][k] - (s[i] != t[j]) * 5;
            p[l] = s[i], q[l] = t[j];
            i--; j--;
            k = (f[i][j][0] == o) ? 0 : (f[i][j][1] == o ? 1 : 2);
        } else if (k == 1) {
            int o = f[i][j][k];
            p[l] = s[i], q[l] = '-';
            i--;
            k = (f[i][j][0] + 9 == o) ? 0 : (f[i][j][1] + 2 == o ? 1 : 2);
        } else {
            int o = f[i][j][k];
            p[l] = '-', q[l] = t[j];
            j--;
            k = (f[i][j][0] + 9 == o) ? 0 : (f[i][j][1] + 9 == o ? 1 : 2);
        }
        l++;
    }
    printf("%d\n", ans);
    for (int i = l - 1; i >= 0; --i) {
        putchar(p[i]);
    }
    puts("");
    for (int i = l - 1; i >= 0; --i) {
        putchar(q[i]);
    }
    puts("");
}

int main(){
    int T = 1;
    for (int i = 1; i <= T; i++)
        solve(i);
    return 0;
}