不完全AC。

错 Substack #1 的 11、17 号测试点

//#pragma GCC optimize (2)
#include <bits/stdc++.h>
#define int long long

using namespace std;
const int N = 2e3 + 5e2 + 5;
const int M = 2e4 + 5;
const int INF = -1e16;

int read () {
	int x = 0, y = 1;
	char c = getchar ();
	while (c < '0' || c > '9') {
		if (c == '-')	y = -1;
		c = getchar ();
	}
	while (c >= '0' && c <= '9') {
		x = (x << 3) + (x << 1) + c - '0';
		c = getchar ();
	}
	return x * y;
}

void write (int x) {
	if (x < 0)	putchar ('-'), x = -x;
	if (x > 9)	write (x / 10);
	putchar (x % 10 + '0');
}

int n, m, k, cnt, ans;
int head[N];
struct node {	// 链式前向星
	int v, w;
	int nxt;
};
node a[M];
int s[N];	// 点权
int f[4][N], dis[N][N];	// f[k][i] 表示从1出发到i号经过一个点的编号u（点权为所有可能u的第k大）
bool vis[N][N];	

void add (int u, int v, int w) {
	a[ ++ cnt].nxt = head[u];
	a[cnt].v = v;
	a[cnt].w = w;
	head[u] = cnt;
}

void bfs (int s) {	// dis 表示最短路
	queue <int> q;
	q.push (s);
	dis[s][s] = 0;
	while (!q.empty ()) {
		int u = q.front ();
		q.pop ();
		for (int i = head[u]; i; i = a[i].nxt) {
			int v = a[i].v;
			if (!vis[s][v]) {
				dis[s][v] = dis[s][u] + 1;
				vis[s][v] = true;
				q.push (v);
			}
		}
	}
}

void init (int u) {	// 寻找 f[k][i]
	for (int i = 2; i <= n; i ++ ) {
		if (i == u)	continue;
		if (dis[1][i] <= k + 1 && dis[1][i] != 0 && dis[u][i] <= k + 1 && dis[u][i] != 0) {
			if (s[i] > s[f[1][u]]) {
				f[3][u] = f[2][u];
				f[2][u] = f[1][u];
				f[1][u] = i;
			} else if (s[i] > s[f[2][u]]) {
				f[3][u] = f[2][u];
				f[2][u] = i;
			} else if (s[i] > s[f[3][u]]) {
				f[3][u] = i;
			}
		}
	}
}

void fun (int u, int v) {	// 枚举所有 B、C，寻找答案
	if (f[1][u] == 0 || f[1][v] == 0)	return ;
	int j;
	for (int i = 1; i <= 3; i ++ ) {
		if (f[i][u] == v)	continue;
		j = 1;
		while (f[j][v] == f[i][u] || f[j][v] == u)	j ++ ;	// A不能与C、D相同
		ans = max (ans, s[f[i][u]] + s[u] + s[v] + s[f[j][v]]);
	}
}
 
signed main () {
	n = read (), m = read (), k = read ();
	for (int i = 1; i < n; i ++ )	s[i + 1] = read ();
	for (int i = 1; i <= m; i ++ ) {
		int u = read (), v = read (), w = 1;
		add (u, v, w), add (v, u, w);
	}
	
	s[0] = INF;
	for (int i = 1; i <= n; i ++ )	bfs (i);
	for (int i = 2; i <= n; i ++ )	init (i);
	
	for (int i = 2; i <= n; i ++ ) {
		for (int j = 2; j <= n; j ++ ) {
			if (i == j)	continue;
			if (dis[i][j] <= k + 1 && dis[i][j] != 0)	fun (i, j);
		}
	}
	
	write (ans);
	putchar ('\n');
	
	return 0;
}