import java.util.*;
import java.io.*;
 
public class Main {
    static List<Integer>[] tree;
    static char[] color;
    static long[] weight;
    static long minCost = Long.MAX_VALUE;
 
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        color = br.readLine().trim().toCharArray();
        weight = new long[n];
        StringTokenizer st = new StringTokenizer(br.readLine());
        for (int i = 0; i < n; i++) {
            weight[i] = Long.parseLong(st.nextToken());
        }
 
        tree = new ArrayList[n];
        for (int i = 0; i < n; i++) tree[i] = new ArrayList<>();
        for (int i = 0; i < n - 1; i++) {
            st = new StringTokenizer(br.readLine());
            int u = Integer.parseInt(st.nextToken()) - 1;
            int v = Integer.parseInt(st.nextToken()) - 1;
            tree[u].add(v);
            tree[v].add(u);
        }
 
        // 遍历每个节点作为可能的根节点
        for (int root = 0; root < n; root++) {
            char target = color[root];
            long[] totalCost = new long[1];
            boolean[] visited = new boolean[n];
            dfs(root, -1, target, totalCost, visited);
            minCost = Math.min(minCost, totalCost[0]);
        }
 
        System.out.println(minCost);
    }
 
    // 返回是否需要修改该子树
    static boolean dfs(int node, int parent, char target, long[] totalCost, boolean[] visited) {
        visited[node] = true;
        boolean needModify = (color[node] != target);
        long subtreeWeight = weight[node];
 
        for (int child : tree[node]) {
            if (child != parent && !visited[child]) {
                boolean childNeedModify = dfs(child, node, target, totalCost, visited);
                if (childNeedModify) {
                    needModify = true;
                }
                subtreeWeight += weight[child];
            }
        }
 
        if (needModify && parent != -1) { // 非根节点才需要计算修改代价
            totalCost[0] += subtreeWeight;
        }
        return needModify;
    }
}

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4
RGBR
3 1 2 4
1 2
2 3
2 4