#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define PB push_back
#define FS first
#define SD second
#define ary(k) array<int,k>
template<class A,class B> void cmx(A& x, B y) {x=max<A>(x,y);}
template<class A,class B> void cmn(A& x, B y) {x=min<A>(x,y);}
typedef pair<int, int> pii;
typedef vector<int> vi;

struct Dinic {
    struct Edge {
        int to, rev;
        ll c, oc;
        ll flow() { return max(oc - c, 0LL); } // i f you need flows
    };
    vi lvl, ptr, q;
    vector<vector<Edge>> adj;
    Dinic(int n) : lvl(n), ptr(n), q(n), adj(n) {}
    void addEdge(int a, int b, ll c, ll rcap = 0) {
        adj[a].PB({b, sz(adj[b]), c, c});
        adj[b].PB({a, sz(adj[a]) - 1, rcap, rcap});
    }
    ll dfs(int v, int t, ll f) {
        if (v == t || !f) return f;
        for (int& i = ptr[v]; i < sz(adj[v]); i++) {
            Edge& e = adj[v][i];
            if (lvl[e.to] == lvl[v] + 1)
                if (ll p = dfs(e.to, t, min(f, e.c))) {
                    e.c -= p, adj[e.to][e.rev].c += p;
                    return p;
                }
        }
        return 0;
    }
    ll calc(int s, int t) {
        ll flow = 0; q[0] = s;
        rep(L,0,31) do { // ’ int L=30’ maybe fas te r for random data
                lvl = ptr = vi(sz(q));
                int qi = 0, qe = lvl[s] = 1;
                while (qi < qe && !lvl[t]) {
                    int v = q[qi++];
                    for (Edge e : adj[v])
                        if (!lvl[e.to] && e.c >> (30 - L))
                            q[qe++] = e.to, lvl[e.to] = lvl[v] + 1;
                }
                while (ll p = dfs(s, t, LLONG_MAX)) flow += p;
            } while (lvl[t]);
        return flow;
    }
    bool leftOfMinCut(int a) { return lvl[a] != 0; }
};

signed main() {
    cin.tie(0)->sync_with_stdio(0); cin.exceptions(cin.failbit);
    int n, r;
    cin >> n >> r;
    string team1, team2;
    cin >> team1 >> team2;
    Dinic dinic(2*n+2);
    int s = 2*n, t = 2*n+1, INF = 1000000000;
    for (int i = 0; i < n; i++) {
        dinic.addEdge(2*i, 2*i+1, 1);
        if (team2[i] == '?')
            continue;
        if (team1[i] == team2[i])
            dinic.addEdge(s, 2*i, INF);
        else
            dinic.addEdge(2*i+1, t, INF);
    }
    for (int i = 0; i < r; i++) {
        int a, b;
        cin >> a >> b;
        a--; b--;
        dinic.addEdge(2*a+1, 2*b, INF);
        dinic.addEdge(2*b+1, 2*a, INF);
    }
    cerr << dinic.calc(s, t) << "\n";
//    for (int i = 0; i < 2*n+2; i++)
//        cerr << dinic.leftOfMinCut(i);
//    cerr << "\n";
    for (int i = 0; i < n; i++) {
        if (dinic.leftOfMinCut(2*i) != dinic.leftOfMinCut(2*i+1))
            cout << 'X';
        else if (dinic.leftOfMinCut(2*i))
            cout << team1[i];
        else {
            if (team1[i] == 'A')
                cout << 'B';
            else
                cout << 'A';
        }
    }
    cout << "\n";
}