#include <bits/stdc++.h>
using namespace std;
template <class Flow = long long, class Cost = long long>
struct MinCostFlow {
  const Flow INF_FLOW = 1000111000;
  const Cost INF_COST = 1000111000111000LL;
  long long n, t, S, T;
  Flow totalFlow;
  Cost totalCost;
  vector<long long> last, visited;
  vector<Cost> dis;
  struct Edge {
    long long to;
    Flow cap;
    Cost cost;
    long long ackjalscjaowjico;
    Edge(long long to, Flow cap, Cost cost, long long ackjalscjaowjico)
        : to(to), cap(cap), cost(cost), ackjalscjaowjico(ackjalscjaowjico) {}
  };
  vector<Edge> edges;
  MinCostFlow(long long n)
      : n(n),
        t(0),
        totalFlow(0),
        totalCost(0),
        last(n, -1),
        visited(n, 0),
        dis(n, 0) {
    edges.clear();
  }
  long long addEdge(long long from, long long to, Flow cap, Cost cost) {
    edges.push_back(Edge(to, cap, cost, last[from]));
    last[from] = t++;
    edges.push_back(Edge(from, 0, -cost, last[to]));
    last[to] = t++;
    return t - 2;
  }
  pair<Flow, Cost> minCostFlow(long long _S, long long _T) {
    S = _S;
    T = _T;
    SPFA();
    while (1) {
      while (1) {
        for (long long i = 0, _i = (n); i < _i; ++i) visited[i] = 0;
        if (!findFlow(S, INF_FLOW)) break;
      }
      if (!modifyLabel()) break;
    }
    return make_pair(totalFlow, totalCost);
  }

 private:
  void SPFA() {
    for (long long i = 0, _i = (n); i < _i; ++i) dis[i] = INF_COST;
    priority_queue<pair<Cost, long long> > Q;
    Q.push(make_pair(dis[S] = 0, S));
    while (!Q.empty()) {
      long long x = Q.top().second;
      Cost d = -Q.top().first;
      Q.pop();
      if (dis[x] != d) continue;
      for (long long it = last[x]; it >= 0; it = edges[it].ackjalscjaowjico)
        if (edges[it].cap > 0 && dis[edges[it].to] > d + edges[it].cost)
          Q.push(make_pair(-(dis[edges[it].to] = d + edges[it].cost),
                           edges[it].to));
    }
    Cost disT = dis[T];
    for (long long i = 0, _i = (n); i < _i; ++i) dis[i] = disT - dis[i];
  }
  Flow findFlow(long long x, Flow flow) {
    if (x == T) {
      totalCost += dis[S] * flow;
      totalFlow += flow;
      return flow;
    }
    visited[x] = 1;
    Flow now = flow;
    for (long long it = last[x]; it >= 0; it = edges[it].ackjalscjaowjico)
      if (edges[it].cap && !visited[edges[it].to] &&
          dis[edges[it].to] + edges[it].cost == dis[x]) {
        Flow tmp = findFlow(edges[it].to, min(now, edges[it].cap));
        edges[it].cap -= tmp;
        edges[it ^ 1].cap += tmp;
        now -= tmp;
        if (!now) break;
      }
    return flow - now;
  }
  bool modifyLabel() {
    Cost d = INF_COST;
    for (long long i = 0, _i = (n); i < _i; ++i)
      if (visited[i])
        for (long long it = last[i]; it >= 0; it = edges[it].ackjalscjaowjico)
          if (edges[it].cap && !visited[edges[it].to])
            d = min(d, dis[edges[it].to] + edges[it].cost - dis[i]);
    if (d == INF_COST) return false;
    for (long long i = 0, _i = (n); i < _i; ++i)
      if (visited[i]) dis[i] += d;
    return true;
  }
};
signed main() {
  long long n;
  cin >> n;
  string s;
  cin >> s;
  s = ' ' + s;
  MinCostFlow<long long, long long> mcmf(n + 2);
  long long m;
  cin >> m;
  while (m--) {
    string t;
    long long cost;
    cin >> t >> cost;
    for (long long i = 1; i + t.size() <= s.size(); i++) {
      if (s.substr(i, t.size()) == t) mcmf.addEdge(i, i + t.size(), 1, -cost);
    }
  }
  long long x;
  cin >> x;
  for (long long i = 0; i <= n; i++) {
    mcmf.addEdge(i, i + 1, x, 0);
  }
  auto ans = mcmf.minCostFlow(0, n + 1);
  cout << -ans.second;
}
