#include <iostream>
#include <string>
#include <cassert>
#include <algorithm>
using namespace std;

// 0 : 挿入も削除もしない
// 1 : 挿入した
// 2 : 削除した
int dp[1300][1300][3];

int main() {
	int n, m;
	string S, T;
	cin >> n >> m;
	cin >> S >> T;
	for(int i = 0; i <= T.size(); i++) {
		dp[0][i][0] = 1e9;
		dp[0][i][1] = 9 + (i-1)*2;
		dp[0][i][2] = 1e9;
	}
	for(int i = 0; i <= S.size(); i++) {
		dp[i][0][0] = 1e9;
		dp[i][0][1] = 1e9;
		dp[i][0][2] = 9 + (i-1)*2;
	}
	dp[0][0][0] = 0;
	dp[0][0][1] = 1e9;
	dp[0][0][2] = 1e9;
	for(int i = 0; i < S.size(); i++) {
		for(int j = 0; j < T.size(); j++) {
			dp[i+1][j+1][0] = min(min(dp[i][j][0], dp[i][j][1]),
					dp[i][j][2]) + (S[i]==T[j] ? 0 : 5);
			dp[i+1][j+1][1] = min(dp[i+1][j][0] + 9,
					min(dp[i+1][j][1] + 2, dp[i+1][j][2] + 9));
			dp[i+1][j+1][2] = min(dp[i][j+1][0] + 9,
					min(dp[i][j+1][1] + 9, dp[i][j+1][2] + 2));
		}
	}
	int res = 1e9;
	int act;
	for(int i = 0; i < 3; i++) {
		if(res > dp[n][m][i]) {
			res = dp[n][m][i];
			act = i;
		}
	}
	
	string rS = "", rT = "";
	while(n+m) {
		if(act == 0) {
			for(int i = 0; i < 3; i++) {
				if(dp[n][m][act] == dp[n-1][m-1][i] + (S[n-1] == T[m-1] ? 0 : 5)) {
					act = i;
					break;
				}
			}
			n--; m--;
			rS += S[n];
			rT += T[m];
		}
		else if (act == 1){
			for(int i = 0; i < 3; i++) {
				if(dp[n][m][act] == dp[n][m-1][i] + (act == i ? 2 : 9)) {
					act = i;
					break;
				}
			}
			m--;
			rS += "-";
			rT += T[m];
		}
		else {
			for(int i = 0; i < 3; i++) {
				if(dp[n][m][act] == dp[n-1][m][i] + (act == i ? 2 : 9)) {
					act = i;
					break;
				}
			}
			n--;
			rS += S[n];
			rT += "-";
		}
	}
	reverse(rS.begin(), rS.end());
	reverse(rT.begin(), rT.end());
	cout << res << endl;
	cout << rS << endl;
	cout << rT << endl;
}