/*
                                                                                
                                   ### #                                        
                              ############# #                                   
                          #######################                               
                     ################################                           
                 #########################################                      
              ##############################################                    
             #     #####################################     #                  
            ######     ############################     ######                  
            ###########     ###################   # ##########                  
            ################    #########      ###############                  
            ####################        # ####################                  
            #######   ##############  ########################                  
            ########       #########  ########################                  
            ###########      #######  ########################                  
            ############## # #######  ########################                  
            ########################  ########################                  
            ########################  ########################                  
            ########################  ########################                  
              ######################  #######################                   
                 ###################  ###################                       
                      ##############  ###############                           
                          ##########  ##########                                
                              ######  ######                                    
                                  ##  ##                                        
                                                                                
                                                                                
                                                                                
                        #                             #                         
                        #      #                      #                         
        #    #  #    #  #   #      ####   ####     ####   ####   ####           
         #   #  #    #  # ##   #  #      #    #  #    #  #____#  ##             
          # #/  #    #  ## #   #  #      #    #  #    #  #^^^^   #              
           ##    ###/#  #   #  #   ####   ####    ###/#   ####   #              
           #                                                                    
         ##                                                                     
                                                                                
*/

#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <functional>
#include <set>
#include <ctime>
#include <random>
#include <chrono>
#include <cassert>
using namespace std;

namespace {
  using Integer = long long; //__int128;
  template<class T> istream& operator >> (istream& is, vector<T>& vec){for(T& val: vec) is >> val; return is;}
  template<class T> istream& operator ,  (istream& is, T& val){ return is >> val;}
  template<class T> ostream& operator << (ostream& os, const vector<T>& vec){for(int i=0; i<vec.size(); i++) os << vec[i] << (i==vec.size()-1?"":" "); return os;}
  template<class T> ostream& operator ,  (ostream& os, const T& val){ return os << " " << val;}

  template<class H> void print(const H& head){ cout << head; }
  template<class H, class ... T> void print(const H& head, const T& ... tail){ cout << head << " "; print(tail...); }
  template<class ... T> void println(const T& ... values){ print(values...); cout << endl; }

  template<class H> void eprint(const H& head){ cerr << head; }
  template<class H, class ... T> void eprint(const H& head, const T& ... tail){ cerr << head << " "; eprint(tail...); }
  template<class ... T> void eprintln(const T& ... values){ eprint(values...); cerr << endl; }

  class range{
    long long start_, end_, step_;
   public:
    struct range_iterator{
      long long val, step_;
      range_iterator(long long v, long long step) : val(v), step_(step) {}
      long long operator * (){return val;}
      void operator ++ (){val += step_;}
      bool operator != (range_iterator& x){return step_ > 0 ? val < x.val : val > x.val;}
    };
    range(long long len) : start_(0), end_(len), step_(1) {}
    range(long long start, long long end) : start_(start), end_(end), step_(1) {}
    range(long long start, long long end, long long step) : start_(start), end_(end), step_(step) {}
    range_iterator begin(){ return range_iterator(start_, step_); }
    range_iterator   end(){ return range_iterator(  end_, step_); }
  };

  string operator "" _s (const char* str, size_t size){ return move(string(str)); }
  constexpr Integer my_pow(Integer x, Integer k, Integer z=1){return k==0 ? z : k==1 ? z*x : (k&1) ? my_pow(x*x,k>>1,z*x) : my_pow(x*x,k>>1,z);}
  constexpr Integer my_pow_mod(Integer x, Integer k, Integer M, Integer z=1){return k==0 ? z%M : k==1 ? z*x%M : (k&1) ? my_pow_mod(x*x%M,k>>1,M,z*x%M) : my_pow_mod(x*x%M,k>>1,M,z);}
  constexpr unsigned long long operator "" _ten (unsigned long long value){ return my_pow(10,value); }

  inline int k_bit(Integer x, int k){return (x>>k)&1;} //0-indexed

  mt19937 mt(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count());

  template<class T> string join(const vector<T>& v, const string& sep){
    stringstream ss; for(int i=0; i<v.size(); i++){ if(i>0) ss << sep; ss << v[i]; } return ss.str();
  }

  string operator * (string s, int k){ string ret; while(k){ if(k&1) ret += s; s += s; k >>= 1; } return ret; }

}

constexpr long long mod = 9_ten + 7;

int main(){
  int n,m;
  cin >> n,m;
  string s,t;
  cin >> s,t;

  vector<vector<vector<pair<int,int>>>> dp(m+1, vector<vector<pair<int,int>>>(n+1,
    vector<pair<int,int>>(3, {1e8, 0})));

  vector<vector<vector< vector<int> >>> dp_last(m+1, vector<vector< vector<int> >>(n+1,
    vector< vector<int> >(3)));
  dp[0][0][0] = {0,0};

  for(int i=0; i<=m; i++){
    for(int j=0; j<=n; j++){
      if(j<n && i<m){
        if(s[j] == t[i]){ //use
          if( dp[i+1][j+1][0] >  dp[i][j][0] ){
            dp[i+1][j+1][0] = dp[i][j][0];
            dp_last[i+1][j+1][0] = {i,j,0};
          }
          if( dp[i+1][j+1][0] > pair<int,int>{dp[i][j][1].first, j} ){
            dp[i+1][j+1][0] = {dp[i][j][1].first, j};
            dp_last[i+1][j+1][0] = {i,j,1};
          }
          if( dp[i+1][j+1][0] > pair<int,int>{dp[i][j][2].first, i} ){
            dp[i+1][j+1][0] = {dp[i][j][2].first, i};
            dp_last[i+1][j+1][0] = {i,j,2};
          }
        }else{ //replace
          if( dp[i+1][j+1][0] > pair<int,int>{dp[i][j][0].first + 5, dp[i][j][0].second} ){
            dp[i+1][j+1][0] = {dp[i][j][0].first + 5, dp[i][j][0].second};
            dp_last[i+1][j+1][0] = {i,j,0};
          }
          if( dp[i+1][j+1][0] > pair<int,int>{dp[i][j][1].first + 5, j} ){
            dp[i+1][j+1][0] = {dp[i][j][1].first + 5, j};
            dp_last[i+1][j+1][0] = {i,j,1};
          }
          if( dp[i+1][j+1][0] > pair<int,int>{dp[i][j][2].first + 5, i} ){
            dp[i+1][j+1][0] = {dp[i][j][2].first + 5, i};
            dp_last[i+1][j+1][0] = {i,j,2};
          }
        }
      }
      //skip(delete)
      if( j+1 <= n ){
        if( dp[i][j+1][1] > pair<int,int>{dp[i][j][0].first+9, j} ){
          dp[i][j+1][1] = {dp[i][j][0].first+9, j};
          dp_last[i][j+1][1] = {i,j,0};
        }
        if( dp[i][j+1][1] > pair<int,int>{dp[i][j][1].first+2, dp[i][j][1].second} ){
          dp[i][j+1][1] = {dp[i][j][1].first+2, dp[i][j][1].second};
          dp_last[i][j+1][1] = {i,j,1};
        }
        if( dp[i][j+1][1] > pair<int,int>{dp[i][j][2].first+9, j} ){
          dp[i][j+1][1] = {dp[i][j][2].first+9, j};
          dp_last[i][j+1][1] = {i,j,2};
        }
      }

      //skip(insert)
      if(i+1 <= m){
        if(dp[i+1][j][2] > pair<int,int>{dp[i][j][0].first+9, i} ){
          dp[i+1][j][2] = {dp[i][j][0].first+9, i};
          dp_last[i+1][j][2] = {i,j,0};
        }
        if(dp[i+1][j][2] > pair<int,int>{dp[i][j][1].first+9, i} ){
          dp[i+1][j][2] = {dp[i][j][1].first+9, i};
          dp_last[i+1][j][2] = {i,j,1};
        }
        if(dp[i+1][j][2] > pair<int,int>{dp[i][j][2].first+2, dp[i][j][2].second} ){
          dp[i+1][j][2] = {dp[i][j][2].first+2, dp[i][j][2].second};
          dp_last[i+1][j][2] = {i,j,2};
        }
      }
    }
  }

  int state = min_element( dp[m][n].begin(), dp[m][n].end()) - dp[m][n].begin();
  int a = m;
  int b = n;

  int ans = dp[m][n][state].first;

  string ans_s, ans_t;
  while( !(a==0 && b==0) ){
    auto tmp = dp_last[a][b][state];
    if(tmp[0] != a) ans_t += t[a-1];
    if(tmp[1] != b) ans_s += s[b-1];

    if(state == 1){
      ans_t += '-';
    }else if(state==2){
      ans_s += '-';
    }

    a = tmp[0];
    b = tmp[1];
    state = tmp[2];
  }

  //println(a,b);

  println(ans);
  reverse(ans_s.begin(), ans_s.end());
  reverse(ans_t.begin(), ans_t.end());
  println(ans_s);
  println(ans_t);

  return 0;
}