#include <bits/stdc++.h>
using namespace std;
inline void read(int &x) {
  int v = 0, f = 1;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
inline void read(long long &x) {
  long long v = 0ll, f = 1ll;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
inline void readc(char &x) {
  char c;
  while ((c = getchar()) == ' ')
    ;
  x = c;
}
inline void writes(string s) { puts(s.c_str()); }
inline void writeln() { writes(""); }
inline void writei(int x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
inline void writell(long long x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
int n, m, i, j, v, dis[505], cnt, cst, vis[505];
string st, s;
struct edg {
  int y, z, d;
} ee[18005];
vector<int> e[505];
void add(int x, int y, int z, int d) {
  cnt++;
  e[x].push_back(cnt * 2 - 2);
  e[y].push_back(cnt * 2 - 1);
  ee[cnt * 2 - 2] = (edg){y, z, d};
  ee[cnt * 2 - 1] = (edg){x, 0, -d};
}
bool bfs(int s, int t) {
  memset(dis, -18, sizeof(dis));
  dis[s] = 0;
  queue<int> q;
  q.push(s);
  while (!q.empty()) {
    int x = q.front();
    q.pop();
    for (__typeof((e[x]).begin()) it = (e[x]).begin(); it != (e[x]).end();
         it++) {
      if (ee[*it].z == 0) continue;
      int y = ee[*it].y, z = dis[x] + ee[*it].d;
      if (dis[y] < z) {
        dis[y] = z;
        q.push(y);
      }
    }
  }
  return dis[t] > dis[504];
}
int dfs(int x, int t, int flw) {
  if (!flw || (x != t && vis[x])) return 0;
  if (x == t) {
    vis[x] = 1;
    return flw;
  }
  vis[x] = 1;
  int ans = 0;
  for (__typeof((e[x]).begin()) it = (e[x]).begin(); it != (e[x]).end(); it++) {
    if (ee[*it].z == 0) continue;
    int y = ee[*it].y;
    if (dis[y] == dis[x] + ee[*it].d) {
      int tt = dfs(y, t, min(flw, ee[*it].z));
      ans += tt;
      flw -= tt;
      ee[*it].z -= tt;
      ee[(*it) ^ 1].z += tt;
      cst += tt * ee[*it].d;
    }
  }
  return ans;
}
int dinic(int s, int t) {
  int ans = 0;
  while (bfs(s, t)) {
    do {
      memset(vis, 0, sizeof(vis));
      ans += dfs(s, t, 0x3bbbbbbb);
    } while (vis[t]);
  }
  return cst;
}
int main() {
  ios_base::sync_with_stdio(false);
  ;
  cin >> n >> st >> m;
  st = " " + st;
  for (((i)) = (1); ((i)) <= ((n)); ((i))++) add(i, i + 1, 0x3bbbbbbb, 0);
  while (m--) {
    cin >> s >> v;
    for (((i)) = (1); ((i)) <= ((n - ((int)(s.length())) + 1)); ((i))++) {
      if (st.substr(i, s.length()) == s) {
        add(i, i + s.length(), 1, v);
      }
    }
  }
  cin >> v;
  add(0, 1, v, 0);
  cout << dinic(0, n + 1) << endl;
  return 0;
}
