#include <bits/stdc++.h>
using namespace std;
struct MCMF {
  using F = int;
  const static F INF = 0x3f3f3f3f;
  struct Edge {
    int v, bro;
    F cap, cost;
    Edge() {}
    Edge(int _v, int _bro, F _cap, F _cost)
        : v(_v), bro(_bro), cap(_cap), cost(_cost) {}
  };
  vector<Edge> e;
  vector<int> pos, pre;
  vector<F> dis;
  vector<bool> trk;
  int n, s, t, m;
  MCMF(int _n, int _s, int _t) : n(_n), s(_s), t(_t), m(0) {
    pos.assign(n, -1);
    pre.resize(n);
    dis.resize(n);
    trk.resize(n);
    e.reserve(4e5);
  }
  void add(int u, int v, F cap = INF, F cost = 0) {
    assert(u < n && v < n);
    e.emplace_back(v, pos[u], cap, cost);
    pos[u] = m++;
    e.emplace_back(u, pos[v], 0, -cost);
    pos[v] = m++;
  }
  bool spfa() {
    queue<int> q;
    fill(pre.begin(), pre.end(), -1);
    fill(dis.begin(), dis.end(), INF);
    fill(trk.begin(), trk.end(), false);
    dis[s] = 0;
    trk[s] = true;
    q.push(s);
    while (!q.empty()) {
      int u = q.front();
      q.pop();
      trk[u] = false;
      for (int i = pos[u]; i != -1; i = e[i].bro) {
        int v = e[i].v;
        if (e[i].cap > 0 && dis[v] > dis[u] + e[i].cost) {
          dis[v] = dis[u] + e[i].cost;
          pre[v] = i;
          if (!trk[v]) {
            trk[v] = true;
            q.push(v);
          }
        }
      }
    }
    return pre[t] != -1;
  }
  pair<F, F> mcmf() {
    F flow = 0, cost = 0;
    while (spfa()) {
      F f = INF;
      for (int i = pre[t]; i != -1; i = pre[e[i ^ 1].v]) f = min(f, e[i].cap);
      for (int i = pre[t]; i != -1; i = pre[e[i ^ 1].v]) {
        e[i].cap -= f;
        e[i ^ 1].cap += f;
        cost += e[i].cost * f;
      }
      flow += f;
    }
    return {flow, cost};
  }
};
void solve() {
  int n1, n2, m, r, b;
  cin >> n1 >> n2 >> m >> r >> b;
  string s1, s2;
  cin >> s1 >> s2;
  int L = n1 + n2, R = L + 1;
  int S = R + 1, T = S + 1;
  MCMF g(T + 1, S, T);
  vector<int> deg(S), demand(S);
  for (int _ = 0; _ < m; _++) {
    int x, y;
    cin >> x >> y;
    x--;
    y--;
    y += n1;
    deg[x]++;
    deg[y]++;
    demand[x]++;
    demand[y]--;
    g.add(x, y, 1, r);
    g.add(y, x, 1, b);
  }
  auto gg = []() {
    cout << -1;
    exit(0);
  };
  for (int i = 0; i < n1; i++) {
    if (s1[i] != 'U' && deg[i] == 0) gg();
    if (s1[i] == 'R') {
      g.add(L, i, deg[i] - 1);
      demand[i] -= deg[i] + 1;
      demand[L] += deg[i] + 1;
    } else if (s1[i] == 'B') {
      g.add(L, i, deg[i] - 1);
    } else {
      g.add(L, i, deg[i] << 1);
    }
  }
  for (int i = 0; i < n2; i++) {
    int k = i + n1;
    if (s2[i] != 'U' && deg[k] == 0) gg();
    if (s2[i] == 'B') {
      g.add(k, R, deg[k] - 1);
    } else if (s2[i] == 'R') {
      g.add(k, R, deg[k] - 1);
      demand[k] += deg[k] + 1;
      demand[R] -= deg[k] + 1;
    } else {
      g.add(k, R, deg[k] << 1);
    }
  }
  g.add(R, L);
  int sum = 0;
  for (int i = 0; i < S; i++) {
    if (demand[i] > 0) {
      sum += demand[i];
      g.add(i, T, demand[i]);
    }
    if (demand[i] < 0) {
      g.add(S, i, -demand[i]);
    }
  }
  int flow, cost;
  tie(flow, cost) = g.mcmf();
  if (flow < sum) gg();
  cout << cost << "\n";
  for (int i = 0; i < m; i++) {
    if (g.e[i * 4 + 1].cap) {
      cout << 'R';
    } else if (g.e[i * 4 + 3].cap) {
      cout << 'B';
    } else {
      cout << 'U';
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
  return 0;
}
