#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,b) for(int i=0;i<b;i++)
#define rrep(i,b) for(int i=b-1;i>=0;i--)
#define rep1(i,b) for(int i=1;i<b;i++)
#define repx(i,x,b) for(int i=x;i<b;i++)
#define rrepx(i,x,b) for(int i=b-1;i>=x;i--)
#define fore(i,a) for(auto i:a)
#define fore1(i,a) for(auto &i:a)
#define rng(x) (x).begin(), (x).end()
#define rrng(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define fi first
#define se second
#define pcnt __builtin_popcountll

using namespace std;
using namespace atcoder;

using ll = long long;
using ld = long double;
template<typename T> using mpq = priority_queue<T, vector<T>, greater<T>>;
template<typename T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<typename T> bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename T> ll sumv(const vector<T>&a){ll res(0);for(auto&&x:a)res+=x;return res;}
bool yn(bool a) { if(a) {cout << "Yes" << endl; return true;} else {cout << "No" << endl; return false;}}
#define dame { cout << "No" << endl; return;}
#define dame1 { cout << -1 << endl; return;}
#define cout2(x,y) cout << x << " " << y << endl;
#define coutp(p) cout << p.fi << " " << p.se << endl;
#define out cout << ans << endl;
#define outd cout << fixed << setprecision(20) << ans << endl;
#define outm cout << ans.val() << endl;
#define outv fore(yans , ans) cout << yans << "\n";
#define outdv fore(yans , ans) cout << yans.val() << "\n";
#define coutv(v) {fore(vy , v) {cout << vy << " ";} cout << endl;}
#define coutv2(v) fore(vy , v) cout << vy << "\n";
#define coutvm(v) {fore(vy , v) {cout << vy.val() << " ";} cout << endl;}
#define coutvm2(v) fore(vy , v) cout << vy.val() << "\n";
using pll = pair<ll,ll>;using pil = pair<int,ll>;using pli = pair<ll,int>;using pii = pair<int,int>;using pdd = pair<ld,ld>;
using tp = tuple<int ,int ,int>;
using vi = vector<int>;using vd = vector<ld>;using vl = vector<ll>;using vs = vector<string>;using vb = vector<bool>;
using vpii = vector<pii>;using vpli = vector<pli>;using vpll = vector<pll>;using vpil = vector<pil>;
using vvi = vector<vector<int>>;using vvl = vector<vector<ll>>;using vvs = vector<vector<string>>;using vvb = vector<vector<bool>>;
using vvpii = vector<vector<pii>>;using vvpli = vector<vector<pli>>;using vvpll = vector<vpll>;using vvpil = vector<vpil>;
using mint = modint998244353;
//using mint = modint1000000007;
//using mint = dynamic_modint<0>;
using vm = vector<mint>;
using vvm = vector<vector<mint>>;
vector<int> dx={1,0,-1,0,1,1,-1,-1},dy={0,1,0,-1,1,-1,1,-1};
ll gcd(ll a, ll b) { return a?gcd(b%a,a):b;}
ll lcm(ll a, ll b) { return a/gcd(a,b)*b;}
#define yes {cout <<"Yes"<<endl;}
#define yesr { cout <<"Yes"<<endl; return;}
#define no {cout <<"No"<<endl;}
#define nor { cout <<"No"<<endl; return;}
const double eps = 1e-10;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#ifdef MY_LOCAL_DEBUG
#define show(x) cerr<<#x<<" = "<<x<<endl
#define showp(p) cerr<<#p<<" = "<<p.fi<<" : "<<p.se<<endl
#define show2(x,y) cerr<<#x<<" = "<<x<<" : "<<#y<<" = "<<y<<endl
#define show3(x,y,z) cerr<<#x<<" = "<<x<<" : "<<#y<<" = "<<y<<" : "<<#z<<" = "<<z<<endl
#define show4(x,y,z,x2) cerr<<#x<<" = "<<x<<" : "<<#y<<" = "<<y<<" : "<<#z<<" = "<<z<<" : "<<#x2<<" = "<<x2<<endl
#define test(x) cout << "test" << x << endl
#define showv(v) {fore(vy , v) {cout << vy << " ";} cout << endl;}
#define showv2(v) fore(vy , v) cout << vy << "\n";
#define showvm(v) {fore(vy , v) {cout << vy.val() << " ";} cout << endl;}
#define showvm2(v) fore(vy , v) cout << vy.val() << "\n";
#else
#define show(x)
#define showp(p)
#define show2(x,y)
#define show3(x,y,z)
#define show4(x,y,z,x2)
#define test(x)
#define showv(v)
#define showv2(v)
#define showvm(v)
#define showvm2(v)
#endif
struct node{
    map<char,int> nxt_node;
    vi fin_id_list;
    ll word_com_cnt=0;
    ll word_fin_cnt=0;

    node(){}
};
struct Trie{
    int node_num = 0;
    int word_num = 0;
    vector<node> vnode;
    map<string , int> word_id;
    ///// Aho_Corasick ///////
    vs init_v;
    vi fail;
    vi par;
    bool bBuild = false;

    Trie(){
        vnode.pb(node());
        par.pb(-1);
    }

    void insert(string s){
        if (s == "") return;

        word_id[s] = word_num++;

        int now = 0;
        int szs = sz(s);
        rep(i , szs){
            node& tmp = vnode[now];
            tmp.word_com_cnt++;
            if (tmp.nxt_node.count(s[i])){
                now = tmp.nxt_node[s[i]];
            }else{
                tmp.nxt_node[s[i]] = ++node_num;
                vnode.pb(node());
                par.pb(now);
                now = node_num;
            }
        }
        node& tmp = vnode[now];
        tmp.fin_id_list.pb(word_num-1);
        tmp.word_com_cnt++;
        tmp.word_fin_cnt++;
    }

    bool isFind(string s){
        bool ret = true;
        int now = 0;
        int szs = sz(s);
        rep(i,szs){
            const node& tmp = vnode[now];
            if (tmp.nxt_node.count(s[i])) now = tmp.nxt_node.count(s[i]);
            else{
                ret = false;
                break;
            }

            if (i == szs-1){
                ret = (tmp.word_fin_cnt > 0);
            }
        }

        return ret;
    }

    int count(){
        return word_num;
    }

    int size(){
        return node_num;
    }

    int getId(string s){
        assert(word_id.count(s));
        return word_id[s];
    }

    //////////////////////// Aho_Corasick ///////////////////

    void add(string s){
        init_v.pb(s);
    }

    void build(){
        bBuild = true;
        rep(i,sz(init_v)) insert(init_v[i]);
        fail.resize(node_num+1);

        queue<pair<int,char>> q;
        q.push({0,'a'});

        while(!q.empty()){
            int x = q.front().fi;
            char c = q.front().se;
            q.pop();

            node& nx = vnode[x];
            if (x){
                int now = par[x];
                while(now != 0){
                    now = fail[now];
                    node& nown = vnode[now];
                    if (nown.nxt_node.count(c)){
                        fail[x] = nown.nxt_node[c];
                        break;
                    }
                }
                node& nxx2 = vnode[fail[x]];
                nx.word_fin_cnt += nxx2.word_fin_cnt;
            }

            rep(i,26){
                char c = 'a' + i;
                if (nx.nxt_node.count(c)){
                    int y = nx.nxt_node[c];
                    q.push({y,c});
                }
            }
        }
    }

} trie;

/* 
Trie 木 : コンストラクタの引数なし
メンバ関数
insert(word): 単語 word を Trie 木に挿入する
isFind(word): 単語 word が Trie 木にあるか判定する
count(): 挿入した単語の数を返す
size(): Trie 木の頂点数を返す
getId(word): word_idを返す
計算量:insert, isFind ともに O(M)（Mは単語の長さ）

メンバ変数
int node_num = 0: trie木内のノード数
int word_num = 0; 挿入した単語集
vector<node> vnode: ノードidx - ノード
map<string , int> word_id: word - word_id

[Nodeのメンバ変数]ノード自体はnodesに格納されている
map<char,int> nxt_node: 子ノードのword_idリスト
vi fin_id_list:     このノードを終点とするwordのword_idリスト
int word_com_cnt=0: このノードを共有するword数
int word_fin_cnt=0: このノードを終点とするword数

Aho_Corasick
add(word): insert,wordを先読みしておく
build(): addした単語に関して木を構築、failureリンクも貼る
*/

void solve(){
    int n,m; cin>>n>>m;
    string s1; cin>>s1;
    string s2; cin>>s2;

    string s = s1;
    s += 'z' + 1;
    s += s2;
    vi sa = suffix_array(s);
    vi lc = lcp_array(s,sa);
    rep(i,n+m+1){
        if (sa[i] == n+1){
            int mx = 0;
            if (i) chmax(mx , lc[i-1]);
            if (i < n+m) chmax(mx , lc[i]);
            if (mx == m){
                string ans;
                rep(j,n){
                    if (s1[j] == '?') ans += 'a';
                    else ans += s1[j];
                }
                out;
                return;
            }
        }
    }


    reverse(rng(s1));
    reverse(rng(s2));
    trie.add(s2);
    trie.build();

    int now = 0;

    string ans;

    rep(i,n){
        bool ok = false;
        if (s1[i] == '?') ok = true;
        else{
            if (trie.vnode[now].nxt_node.count(s1[i])){
                ok = true;
            }else{
                ok = false;
            }
        }
        if (ok) now++;
        else{
            if (now == 0) continue;
            now = trie.fail[now];
            i--;
        }
        if (now == m){
            reverse(rng(s1));
            reverse(rng(s2));
            rep(j,n-i-1){
                if (s1[j] == '?') ans += 'a';
                else ans += s1[j];
            }
            ans += s2;
            repx(j,n-i-1+m,n){
                if (s1[j] == '?') ans += 'a';
                else ans += s1[j];
            }
            break;
        }
    }
    if (ans == "") dame1;
    out;

    return;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    cin>>t;

    rep(i,t){
        solve();
    }

    return 0;
}