cf274b WA

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#define dbg(...) logger(#__VA_ARGS__, __VA_ARGS__)
template <typename... Args> void logger(string vars, Args &&...values)
{
    cerr << vars << " = ";
    string delim = "";
    (..., (cerr << delim << values, delim = ", "));
    cerr << endl;
}

template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int n;
vector<int> g[100003];
int val[100003];
int vis[100003];

pll dfs(int now)
{
    // op_cnt, op_offset
    vis[now] = 1;
    int out_cnt = 0;
    ll op_acc = 0;
    ll op_offset = 0;
    for (auto out : g[now]) {
        if (vis[out] == 0) {
            auto op = dfs(out);
            op_acc += op.first;
            op_offset += op.second;
            ++out_cnt;
        }
    }
    if (out_cnt == 0) {
        return {abs(val[now]), -val[now]};
    }
    ll new_offset = -(op_offset + val[now]);
    ll new_op_acc = op_acc + abs(new_offset);
    // return {op_acc + abs(val[now] + op_offset), -val[now] + op_offset};
    return {new_op_acc, new_offset};
}

int main(int argc, char **argv)
{
    scanf("%d", &n);
    int a, b;
    for (int i = 1; i < n; ++i) {
        scanf("%d%d", &a, &b);
        g[a].push_back(b);
        g[b].push_back(a);
    }
    for (int i = 1; i <= n; ++i)
        scanf("%d", val + i);
    auto ret = dfs(1);
    printf("%lld\n", ret.first);
    return 0;
};