func_code_string: #include <bits/stdc++.h>   using namespace std;   void Rd(int &x) {     static char c;     x = 0;     while ((c = getchar()) < 48)       ;     do x = (x << 3) + (x << 1) + (c ^ 48);     while ((c = getchar()) > 47);   }   int n;   int Next[200004 << 1], V[200004 << 1], W[200004], Head[200004], tot;   void Add_Edge(int u, int v) { Next[++tot] = Head[u], V[Head[u] = tot] = v; }   int Sz[200004], G, Mn, Nowsz;   bool Mark[200004];   long long Ans, Dis[200004];   void GetG(int x, int f) {     int y, mx = 0;     Sz[x] = 1;     for (int i = Head[x]; i; i = Next[i])       if (!Mark[y = V[i]] && y != f) {         GetG(y, x);         Sz[x] += Sz[y];         mx = max(mx, Sz[y]);       }     mx = max(mx, Nowsz - Sz[x]);     if (mx < Mn) Mn = mx, G = x;   }   int m;   struct Node {     int l;     long long d;   } D[200004];   long long Calc(int x) {     long long Tmp[2] = {0, 0}, Cnt[2] = {0, 0}, Res = 0;     for (int i = (0), i_end_ = (m); i < i_end_; ++i)       (Tmp[D[i].l & 1] += D[i].d) %= 1000000007, Cnt[D[i].l & 1]++;     Res -= 2 * Cnt[1] * Tmp[1] + Cnt[1] * Cnt[1] % 1000000007 * W[x];     Res += 2 * Cnt[0] * Tmp[0] + Cnt[0] * Cnt[0] % 1000000007 * W[x];     return Res % 1000000007;   }   void Gets(int x, int f, int d) {     D[m++] = (Node){d, Dis[x]};     int y;     Sz[x] = 1;     for (int i = Head[x]; i; i = Next[i])       if (!Mark[y = V[i]] && y != f) {         Dis[y] = Dis[x] + ((d & 1) ? W[y] : -W[y]);         Gets(y, x, d + 1);         Sz[x] += Sz[y];       }   }   void Work(int x, int sz) {     Mn = 200004, Nowsz = sz;     GetG(x, 0);     Mark[x = G] = 1;     m = Dis[x] = 0;     Gets(x, 0, 0);     Ans += Calc(x);     if (sz == 1) return;     int y;     for (int i = Head[x]; i; i = Next[i])       if (!Mark[y = V[i]]) {         m = 0;         Gets(y, x, 1);         Ans -= Calc(x);         Work(y, Sz[y]);       }   }   int main() {     Rd(n);     for (int i = (1), i_end_ = (n + 1); i < i_end_; ++i) scanf( %d , &W[i]);     for (int i = (1), i_end_ = (n); i < i_end_; ++i) {       int u, v, w;       Rd(u), Rd(v);       Add_Edge(u, v);       Add_Edge(v, u);     }     Work(1, n);     printf( %I64d n , (Ans % 1000000007 + 1000000007) % 1000000007);     return 0;   }   