#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")

#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
const ll dx[9]={0,1,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
ll base=5000;
ll tr(ll x,ll y,ll z){
    return x*base*base+y*base+z;
}
tuple<ll,ll,ll> rv(ll f){
    tuple<ll,ll,ll> p={f/base/base,(f/base)%base,f%base};
    return p;
}
int main(){
    ll n,m;cin >> n >> m;
    string s,t;cin >> s >> t;
    ll dp[n+1][m+1][3],ndp[n+1][m+1][3];
    rep(i,n+1)rep(j,m+1)rep(k,3)dp[i][j][k]=INF,ndp[i][j][k]=-1;
    dp[0][0][0]=0;
    rep(i,n+1){
        rep(j,m+1){
            if(chmin(dp[i][j][0],dp[i][j][1]))ndp[i][j][0]=tr(i,j,1);
            if(chmin(dp[i][j][0],dp[i][j][2]))ndp[i][j][0]=tr(i,j,2);
            if(chmin(dp[i][j][1],dp[i][j][0]+7))ndp[i][j][1]=tr(i,j,0);
            if(chmin(dp[i][j][2],dp[i][j][0]+7))ndp[i][j][2]=tr(i,j,0);
            if(i<n&&j<m){
                if(s[i]==t[j]){
                    if(chmin(dp[i+1][j+1][0],dp[i][j][0]))ndp[i+1][j+1][0]=tr(i,j,0);
                }
                else {
                    if(chmin(dp[i+1][j+1][0],dp[i][j][0]+5))ndp[i+1][j+1][0]=tr(i,j,0);
                }
            }
            if(i<n){
                if(chmin(dp[i+1][j][1],dp[i][j][1]+2))ndp[i+1][j][1]=tr(i,j,1);
            }
            if(j<m){
                if(chmin(dp[i][j+1][2],dp[i][j][2]+2))ndp[i][j+1][2]=tr(i,j,2);;
            }
        }
    }
    cout << dp[n][m][0] << endl;
    string rs,rt;
    ll x=n,y=m,z=0;
    while(ndp[x][y][z]!=-1){
        auto [nx,ny,nz]=rv(ndp[x][y][z]);
        if(nx!=x&&ny!=y){
            rs+=s[nx],rt+=t[ny];
        }
        else if(nx!=x){
            rs+=s[nx],rt+='-';
        }
        else if(ny!=y){
            rs+='-',rt+=t[ny];
        }
        x=nx,y=ny,z=nz;
    }
    rev(all(rs));rev(all(rt));
    cout << rs << endl;
    cout << rt << endl;
}