#include <bits/stdc++.h>
using namespace std;

const int N = 101;
int K;
vector<int> tree(N);
vector<pair<int, int>> v[N];
int dp[N][N];
int countTree[N][N];

int solve(int x, int k) {
    if (dp[x][k] != -1) {
        return dp[x][k];
    }

    // don't make this node sawmill
    int cost1 = 0;
    int tree1 = tree[x];
    for (auto [i, d]: v[x]) {
        cost1 += solve(i, k);
        cost1 += d * countTree[i][k];
        tree1 += countTree[i][k];
    }

    if (k == K || x == 0) {
        countTree[x][k] = tree1;
        cout << x << " " << k << " -> [10] " << cost1 << " " << tree1 << endl;
        return dp[x][k] = cost1;
    }

    // make this node sawmill
    int cost2 = 0;
    int tree2 = 0;
    for (auto [i, d]: v[x]) {
        cost2 += solve(i, k + 1);
        cost2 += d * countTree[i][k + 1];
        tree2 += countTree[i][k + 1];
    }

    if (cost1 < cost2 || (cost1 == cost2 && tree1 <= tree2)) {
        countTree[x][k] = tree1;
        cout << x << " " << k << " -> [1] "  << cost1 << " " << tree1 << endl;
        return dp[x][k] = cost1;
    } else {
        countTree[x][k] = tree2;
        cout << x << " " << k << " -> [2] " << cost2 << " " << tree2 << endl;
        return dp[x][k] = cost2;
    }
}

int main() {
    int n;
    cin >> n >> K;
    for (int i = 0; i < n; i++) {
        cin >> tree[i];
    }
    for (int i = 0; i < n-1; i++) {
        int x, y, w;
        cin >> x >> y >> w;
        v[y].push_back({x, w});
    }
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= K; j++) {
            dp[i][j] = -1;
            countTree[i][j] = -1;
        }
    }
    cout << solve(0, 0) << endl;
}