#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxn = 505;
const long long inf = 1e15;
struct edge_list {
  int u, v, cap, cost;
};
struct MCMF {
  vector<vector<int>> adj;
  int source, sink;
  vector<edge_list> edge;
  vector<int> trace;
  vector<bool> inqueue;
  vector<long long> dist;
  long long mincost = 0, nflow = 0;
  void init(int sz, int _source, int _sink) {
    sink = _sink, source = _source;
    adj.assign(sz + 5, {});
    trace.resize(sz + 5);
    dist.resize(sz + 5);
    inqueue.resize(sz + 5);
  }
  void modify(void) {
    for (int i = source; i <= sink; ++i) {
      shuffle(adj[i].begin(), adj[i].end(), rng);
    }
  }
  void add_edge(int u, int v, int cap, int cost) {
    adj[u].push_back(edge.size());
    edge.push_back({u, v, cap, cost});
    adj[v].push_back(edge.size());
    edge.push_back({v, u, 0, -cost});
  }
  bool spfa(void) {
    queue<int> Q;
    for (int i = source; i <= sink; ++i) {
      inqueue[i] = 0;
      dist[i] = inf;
    }
    Q.push(source);
    inqueue[source] = 1;
    dist[source] = 0;
    while (Q.size()) {
      int u = Q.front();
      Q.pop();
      inqueue[u] = 0;
      for (int i : adj[u]) {
        if (edge[i].cap > 0 && dist[edge[i].v] > dist[u] + edge[i].cost) {
          dist[edge[i].v] = dist[u] + edge[i].cost;
          trace[edge[i].v] = i;
          if (!inqueue[edge[i].v]) {
            inqueue[edge[i].v] = true;
            Q.push(edge[i].v);
          }
        }
      }
    }
    return dist[sink] < inf;
  }
  void incpath(void) {
    int flow = 1e9;
    for (int u = sink; u != source; u = edge[trace[u]].u) {
      int id = trace[u];
      flow = min(flow, edge[id].cap);
    }
    for (int u = sink; u != source; u = edge[trace[u]].u) {
      int id = trace[u];
      edge[id].cap -= flow;
      edge[id ^ 1].cap += flow;
    }
    mincost += flow * dist[sink];
    nflow += flow;
  }
  void Get(void) {
    while (spfa()) {
      incpath();
    }
  }
} mcmf;
signed main(void) {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  if (fopen("A.INP", "r")) {
    freopen("A.INP", "r", stdin);
    freopen("A.OUT", "w", stdout);
  }
  if (fopen(""
            ".in",
            "r")) {
    freopen(
        ""
        ".in",
        "r", stdin);
    freopen(
        ""
        ".out",
        "w", stdout);
  }
  int N;
  cin >> N;
  string str;
  cin >> str;
  int K;
  cin >> K;
  mcmf.init(N, 0, N + 1);
  while (K--) {
    string s;
    cin >> s;
    int val;
    cin >> val;
    for (int i = 0; i < N - s.size() + 1; ++i) {
      if (str.substr(i, s.size()) == s) {
        mcmf.add_edge(i + 1, i + 1 + s.size(), 1, -val);
      }
    }
  }
  for (int i = 1; i <= N; ++i) {
    mcmf.add_edge(i, i + 1, 1e9, 0);
  }
  int x;
  cin >> x;
  mcmf.add_edge(0, 1, x, 0);
  mcmf.modify();
  mcmf.Get();
  cout << -mcmf.mincost << '\n';
}
