#include <bits/stdc++.h>
using namespace std;
template <typename T, typename C>
class mcmf {
 public:
  static constexpr T eps = (T)1e-9;
  struct edge {
    int from;
    int to;
    T c;
    T f;
    C cost;
  };
  vector<vector<int> > g;
  vector<edge> edges;
  vector<C> d;
  vector<int> q;
  vector<bool> in_queue;
  vector<int> pe;
  int n;
  int st, fin;
  T flow;
  C cost;
  mcmf(int _n, int _st, int _fin) : n(_n), st(_st), fin(_fin) {
    assert(0 <= st && st < n && 0 <= fin && fin < n && st != fin);
    g.resize(n);
    d.resize(n);
    in_queue.resize(n);
    pe.resize(n);
    flow = 0;
    cost = 0;
  }
  void clear_flow() {
    for (const edge &e : edges) {
      e.f = 0;
    }
    flow = 0;
  }
  void add(int from, int to, T forward_cap, T backward_cap, C cost) {
    assert(0 <= from && from < n && 0 <= to && to < n);
    g[from].push_back((int)edges.size());
    edges.push_back({from, to, forward_cap, 0, cost});
    g[to].push_back((int)edges.size());
    edges.push_back({to, from, backward_cap, 0, -cost});
  }
  bool expath() {
    fill(d.begin(), d.end(), numeric_limits<C>::max());
    q.clear();
    q.push_back(st);
    d[st] = 0;
    in_queue[st] = true;
    int beg = 0;
    bool found = false;
    while (beg < (int)q.size()) {
      int i = q[beg++];
      if (i == fin) {
        found = true;
      }
      in_queue[i] = false;
      for (int id : g[i]) {
        const edge &e = edges[id];
        if (e.c - e.f > eps && d[i] + e.cost < d[e.to]) {
          d[e.to] = d[i] + e.cost;
          pe[e.to] = id;
          if (!in_queue[e.to]) {
            q.push_back(e.to);
            in_queue[e.to] = true;
          }
        }
      }
    }
    if (d[fin] >= 0) found = 0;
    if (found) {
      T push = numeric_limits<T>::max();
      int v = fin;
      while (v != st) {
        const edge &e = edges[pe[v]];
        push = min(push, e.c - e.f);
        v = e.from;
      }
      v = fin;
      while (v != st) {
        edge &e = edges[pe[v]];
        e.f += push;
        edge &back = edges[pe[v] ^ 1];
        back.f -= push;
        v = e.from;
      }
      flow += push;
      cost += push * d[fin];
    }
    return found;
  }
  pair<T, C> max_flow_min_cost() {
    while (expath()) {
    }
    return make_pair(flow, cost);
  }
};
const int MG1 = 1e5;
int n1, n2, m, r, b;
string s1, s2;
int eu[200], ev[200], er[200];
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> n1 >> n2 >> m >> r >> b >> s1 >> s2;
  mcmf<int, int> a(n1 + n2 + 2, n1 + n2, n1 + n2 + 1);
  memset(er, -1, sizeof(er));
  for (int i = 0, j = 0; i < m; ++i) {
    cin >> eu[i] >> ev[i], --eu[i], --ev[i];
    if (s1[eu[i]] == 'U' && s2[ev[i]] == 'U') continue;
    if (s1[eu[i]] == 'U' && s2[ev[i]] == 'R') {
      a.add(n1 + n2, n1 + ev[i], 1, 0, r);
      er[i] = j++;
      continue;
    }
    if (s1[eu[i]] == 'U' && s2[ev[i]] == 'B') {
      a.add(n1 + ev[i], n1 + n2 + 1, 1, 0, b);
      er[i] = j++;
      continue;
    }
    if (s1[eu[i]] == 'R' && s2[ev[i]] == 'U') {
      a.add(eu[i], n1 + n2 + 1, 1, 0, r);
      er[i] = j++;
      continue;
    }
    if (s1[eu[i]] == 'B' && s2[ev[i]] == 'U') {
      a.add(n1 + n2, eu[i], 1, 0, b);
      er[i] = j++;
      continue;
    }
    a.add(eu[i], n1 + ev[i], 1, 0, r);
    a.add(n1 + ev[i], eu[i], 1, 0, b);
    er[i] = j;
    j += 2;
  }
  int tmg = 0;
  for (int i = 0; i < n1; ++i) {
    if (s1[i] == 'R') {
      a.add(n1 + n2, i, 1, 0, -MG1);
      a.add(n1 + n2, i, 200, 0, 0);
      tmg -= MG1;
    } else if (s1[i] == 'B') {
      a.add(i, n1 + n2 + 1, 1, 0, -MG1);
      a.add(i, n1 + n2 + 1, 200, 0, 0);
      tmg -= MG1;
    }
  }
  for (int i = 0; i < n2; ++i) {
    if (s2[i] == 'R') {
      a.add(n1 + i, n1 + n2 + 1, 1, 0, -MG1);
      a.add(n1 + i, n1 + n2 + 1, 200, 0, 0);
      tmg -= MG1;
    } else if (s2[i] == 'B') {
      a.add(n1 + n2, n1 + i, 1, 0, -MG1);
      a.add(n1 + n2, n1 + i, 200, 0, 0);
      tmg -= MG1;
    }
  }
  pair<int, int> p = a.max_flow_min_cost();
  int cost = p.second - tmg;
  if (cost >= MG1) {
    cout << -1;
    return 0;
  }
  cout << cost << "\n";
  for (int i = 0; i < m; ++i) {
    if (s1[eu[i]] == 'U' && s2[ev[i]] == 'U') {
      cout << 'U';
      continue;
    }
    if (s1[eu[i]] == 'U' && s2[ev[i]] == 'R') {
      if (a.edges[2 * er[i]].f)
        cout << 'R';
      else
        cout << 'U';
      continue;
    }
    if (s1[eu[i]] == 'U' && s2[ev[i]] == 'B') {
      if (a.edges[2 * er[i]].f)
        cout << 'B';
      else
        cout << 'U';
      continue;
    }
    if (s1[eu[i]] == 'R' && s2[ev[i]] == 'U') {
      if (a.edges[2 * er[i]].f)
        cout << 'R';
      else
        cout << 'U';
      continue;
    }
    if (s1[eu[i]] == 'B' && s2[ev[i]] == 'U') {
      if (a.edges[2 * er[i]].f)
        cout << 'B';
      else
        cout << 'U';
      continue;
    }
    if (a.edges[2 * er[i]].f)
      cout << 'R';
    else if (a.edges[2 * (er[i] + 1)].f)
      cout << 'B';
    else
      cout << 'U';
  }
}
