#include <bits/stdc++.h>

using namespace std;

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

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n, m;
	string s, t;

	cin >> n >> m;
	cin >> s;
	cin >> t;

	for (int i = 0; i <= 1200; i++)
	{
		for (int j = 0; j <= 1200; j++)
		{
      for(int k=0;k<3;k++)
      {
			  dp[i][j][k] = 1e9;
      }
		}
	}

  memset(backtracking,-1,sizeof(backtracking));

  for(int i=1;i<=n;i++)
  {
    dp[i][0][2] = 9 + 2*(i-1);
    backtracking[i][0][2][0] = i-1;
    backtracking[i][0][2][1] = 0;
    backtracking[i][0][2][2] = 2;
  }
   for(int i=1;i<=m;i++)
  {
    dp[0][i][1] = 9 + 2*(i-1);
    backtracking[0][i][1][0] = 0;
    backtracking[0][i][1][1] = i-1;
    backtracking[0][i][1][2] = 1;
  } 

	dp[0][0][0] = 0;

	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= m; j++)
		{
      for(int k=0;k<3;k++)
      {
        if (s[i - 1] == t[j - 1])
        {
          //dp[i][j] = min(dp[i][j], dp[i - 1][j - 1]);
          if(dp[i][j][0] > dp[i-1][j-1][k])
          {
            dp[i][j][0] = dp[i-1][j-1][k];
            backtracking[i][j][0][0] = i-1;
            backtracking[i][j][0][1] = j-1;
            backtracking[i][j][0][2] = k;
          }
          if(k==1)
          {
            if(dp[i][j][1] > dp[i][j-1][k] + 2)
            {
              dp[i][j][1] = dp[i][j-1][k] + 2;
              backtracking[i][j][1][0] = i;
              backtracking[i][j][1][1] = j - 1;
              backtracking[i][j][1][2] = k;
            }
          }
          else
          {
            if(dp[i][j][1] > dp[i][j-1][k] + 9)
            {
              dp[i][j][1] = dp[i][j-1][k] + 9;
              backtracking[i][j][1][0] = i;
              backtracking[i][j][1][1] = j-1;
              backtracking[i][j][1][2] = k;
            }
          }
          if(k==2)
          {
            if(dp[i][j][2] > dp[i-1][j][k] + 2)
            {
              dp[i][j][2] = dp[i-1][j][k] + 2;
              backtracking[i][j][2][0] = i - 1;
              backtracking[i][j][2][1] = j;
              backtracking[i][j][2][2] = k;
            }
          }
          else
          {
            if(dp[i][j][2] > dp[i - 1][j][k] + 9)
            {
              dp[i][j][2] = dp[i - 1][j][k] + 9;
              backtracking[i][j][2][0] = i - 1;
              backtracking[i][j][2][1] = j;
              backtracking[i][j][2][2] = k;
            }
          }            
        }
        else
        {
          /*
          dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + 1);
          dp[i][j] = min(dp[i][j], dp[i - 1][j] + 1);
          dp[i][j] = min(dp[i][j], dp[i][j - 1] + 1);
          */
          if(dp[i][j][0] > dp[i-1][j-1][k] + 5)
          {
            dp[i][j][0] = dp[i-1][j-1][k] + 5;
            backtracking[i][j][0][0] = i-1;
            backtracking[i][j][0][1] = j-1;
            backtracking[i][j][0][2] = k;
          }         
          if(k==1)
          {
            if(dp[i][j][1] > dp[i][j-1][k] + 2)
            {
              dp[i][j][1] = dp[i][j-1][k] + 2;
              backtracking[i][j][1][0] = i;
              backtracking[i][j][1][1] = j - 1;
              backtracking[i][j][1][2] = k;
            }
          }
          else
          {
            if(dp[i][j][1] > dp[i][j-1][k] + 9)
            {
              dp[i][j][1] = dp[i][j-1][k] + 9;
              backtracking[i][j][1][0] = i;
              backtracking[i][j][1][1] = j-1;
              backtracking[i][j][1][2] = k;
            }
          }
          if(k==2)
          {
            if(dp[i][j][2] > dp[i-1][j][k] + 2)
            {
              dp[i][j][2] = dp[i-1][j][k] + 2;
              backtracking[i][j][2][0] = i - 1;
              backtracking[i][j][2][1] = j;
              backtracking[i][j][2][2] = k;
            }
          }
          else
          {
            if(dp[i][j][2] > dp[i - 1][j][k] + 9)
            {
              dp[i][j][2] = dp[i - 1][j][k] + 9;
              backtracking[i][j][2][0] = i - 1;
              backtracking[i][j][2][1] = j;
              backtracking[i][j][2][2] = k;
            }
          }          
        }
      }
		}
	}

  int res = 1e9;
  string A,B;
  int idx = -1;
  int N = n;
  int M = m;

  for(int k=0;k<3;k++)
  {
    if(dp[n][m][k] < res)
    {
      res = dp[n][m][k];
      idx = k;
    }
  }

  while(1)
  {
    if(N==0 && M==0)
    {
      break;
    }
    if(idx==0)
    {
      A = s[N-1] + A;
      B = t[M-1] + B;
    }
    else if(idx==1)
    {
      A = '-' + A;
      B = t[M-1] + B;
    }
    else
    {
      A = s[N-1] + A;
      B = '-' + B;
    }
    int nn = backtracking[N][M][idx][0];
    int nm = backtracking[N][M][idx][1];
    int nidx = backtracking[N][M][idx][2];
    N = nn;
    M = nm;
    idx = nidx;
  }
  
  cout << res << '\n';
  cout << A << '\n';
  cout << B << '\n';

	return 0;
}