Tree with Maximum Cost

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https://codeforces.com/contest/1092/problem/F

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=200000+100;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q,u,v;
vector<int>g[N];
ll a[N],d[N],ans;
void dfs(int s,int rt,int dist){
    d[s]=a[s];
    ans+=a[s]*dist;
    for(int i=0,j=g[s].size();i<j;i++){
		int v=g[s][i];
		if(rt==v)continue;
		dfs(v,s,dist+1);
		d[s]+=d[v];
	}
}

void dfs2(int s,int rt,ll res){
	ans=max(res,ans);
	for(int i=0,j=g[s].size();i<j;i++){
		int v=g[s][i];
		if(rt==v)continue;
		dfs2(v,s,res+d[1]-d[v]*2);
	}
}

int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    scanf("%d",&n);
	for(int i=1;i<=n;i++)
        scanf("%lld",&a[i]);
	for(int i=1;i<n;i++){
		scanf("%d%d",&u,&v);
		g[u].push_back(v);
		g[v].push_back(u);
	}
	dfs(1,0,0);
    dfs2(1,0,ans);
    cout << ans << endl;
    //cout << "Hello world!" << endl;
    return 0;
}