import sys
import bisect
sys.setrecursionlimit(10 ** 6)
def solve():
    it = iter(sys.stdin.buffer.read().split())
    n = int(next(it))
    w = [0] * (n + 1)
    for i in range(1, n + 1):
        w[i] = int(next(it))
    g = [[] for _ in range(n + 1)]
    for _ in range(n - 1):
        u = int(next(it))
        v = int(next(it))
        g[u].append(v)
        g[v].append(u)
    sub = [0] * (n + 1)
    tin = [0] * (n + 1)
    tout = [0] * (n + 1)
    tmr = 0
    stk = [(1, 0, 0)]
    par = [0] * (n + 1)
    while stk:
        v, p, state = stk.pop()
        if state == 0:
            par[v] = p
            tin[v] = tmr
            tmr += 1
            stk.append((v, p, 1))
            for u in reversed(g[v]):
                if u != p:
                    stk.append((u, v, 0))
        else:
            sub[v] = w[v]
            for u in g[v]:
                if u != p:
                    sub[v] += sub[u]
            tout[v] = tmr - 1
    total = sub[1]
    ans = 10 ** 30
    a = [(sub[i], i) for i in range(2, n + 1)]
    a.sort()
    vs = [x[0] for x in a]
    def inside(u, v):
        return tin[v] <= tin[u] <= tout[v]
    for v in range(2, n + 1):
        s = sub[v]
        rest = total - s
        tgt = s // 2
        idx = bisect.bisect_left(vs, tgt)
        for j in range(max(0, idx - 2), min(len(vs), idx + 3)):
            y = vs[j]
            u = a[j][1]
            if u == v:
                continue
            if not inside(u, v):
                continue
            b = [y, s - y, rest]
            b.sort()
            cur = b[2] - b[0]
            if cur < ans:
                ans = cur
        tgt = rest // 2
        idx = bisect.bisect_left(vs, tgt)
        for j in range(max(0, idx - 2), min(len(vs), idx + 3)):
            y = vs[j]
            u = a[j][1]
            if inside(u, v):
                continue
            b = [s, y, rest - y]
            b.sort()
            cur = b[2] - b[0]
            if cur < ans:
                ans = cur
    print(ans)

if __name__ == '__main__':
    solve()