#include <bits/stdc++.h>
using namespace std;
const int N = 30;
const int M = 110;
const int LIT = 2500;
const int INF = 1 << 28;
string s;
int n, m;
int val[N][N];
void init() {
  cin >> n;
  memset(val, 0, sizeof(val));
  for (int i = 1; i <= n; i++) {
    string a, b;
    int v;
    cin >> a >> b >> v;
    int aa = a[0] - 'a';
    int bb = b[0] - 'a';
    val[aa][bb] = v;
  }
}
int dp[M][M][N];
void solve() {
  memset(dp, 0, sizeof(dp));
  for (int i = 0; i < 26; i++) {
    int ch = s[0] - 'a';
    dp[0][1][i] = 0;
    dp[0][0][i] = -INF;
    if (i == ch) dp[0][0][i] = 0;
  }
  for (int i = 1; i < s.size(); i++) {
    int ch = s[i] - 'a';
    for (int j = 0; j <= i + 1; j++) {
      for (int k = 0; k < 26; k++) {
        int Max = -INF;
        if (ch == k && j <= i) {
          for (int p = 0; p < 26; p++) {
            int tmp = dp[i - 1][j][p] + val[p][k];
            Max = max(Max, tmp);
          }
        } else {
          for (int p = 0; j && p < 26; p++) {
            int tmp = dp[i - 1][j - 1][p] + val[p][k];
            Max = max(Max, tmp);
          }
        }
        dp[i][j][k] = Max;
      }
    }
  }
  int out = s.size() - 1, res = -INF;
  for (int i = 0; i <= min(out + 1, m); i++) {
    for (int k = 0; k < 26; k++) {
      res = max(res, dp[out][i][k]);
    }
  }
  cout << res << endl;
}
int main() {
  while (cin >> s >> m) {
    init();
    solve();
  }
}
