func_code_string: #include <bits/stdc++.h>   using namespace std;   int s[200500];   vector<int> gr[200500];   int res[200500];   map<int, map<int, int> > w;   char clr[200500];   vector<int> com;   int sum = 0;   int root = 0;   vector<int> tr[200500];   void dfs(int i) {     clr[i] = 1;     sum += s[i];     for (auto u : gr[i]) {       if (!clr[u]) {         tr[i].push_back(u);         dfs(u);       }     }   }   void go(int i) {     for (auto u : tr[i]) {       go(u);       if (w[i].count(u)) {         res[w[i][u]] = s[u];       } else {         res[w[u][i]] = -s[u];       }       s[i] += s[u];     }   }   int main() {     int n;     cin >> n;     for (int i = 1; i <= n; i++) cin >> s[i];     int m;     cin >> m;     for (int i = 0; i < m; i++) {       int a, b;       cin >> a >> b;       gr[a].push_back(b);       gr[b].push_back(a);       w[a][b] = i;     }     for (int i = 1; i <= n; i++) {       if (!clr[i]) {         root = i;         dfs(i);         if (sum == 0) {           go(i);         } else {           cout <<  Impossible ;           return 0;         }       }     }     cout <<  Possible  << endl;     for (int i = 0; i < m; i++) {       cout << res[i] << endl;     }     return 0;   }   