func_code_string: #include <bits/stdc++.h>   #pragma g++ opitmize(3)   #pragma g++ opitmize(2)   #pragma g++ opitmize( fast )   #pragma g++ opitmize( inline )   using namespace std;   int n, m, head[400010], k = -1, vis[400010], h[400010], tot = 1;   long long a[400010], f[400010], f1;   struct node {     int to, nt, fg;   } edge[1000010];   inline void add(int u, int v, int fg) {     edge[++k].nt = head[u];     head[u] = k;     edge[k].to = v;     edge[k].fg = fg;   }   inline long long fr_dfs(int u, int fa) {     long long tmp = 0, t = 0;     vis[u] = 1;     for (register int i = head[u]; ~i; i = edge[i].nt) {       int v = edge[i].to;       if (v == fa) continue;       if (vis[v]) continue;       tmp = fr_dfs(v, u);       t += tmp;       f[(i / 2) + 1] += tmp * edge[i ^ 1].fg;     }     if (a[u] < 0) {       long long hhd = a[u];       a[u] = 0;       return t + hhd;     }     return t;   }   inline void sc_dfs(int u, int fa, long long &flow) {     if (a[u] > 0) {       flow += a[u];       a[u] = 0;     }     vis[u] = 1;     for (register int i = head[u]; ~i; i = edge[i].nt) {       int v = edge[i].to;       if (v == fa || vis[v]) continue;       f[(i / 2) + 1] += (flow * edge[i].fg);       sc_dfs(v, u, flow);       f[(i / 2) + 1] += (flow * edge[i ^ 1].fg);     }   }   int main() {     memset(head, -1, sizeof(head));     scanf( %d , &n);     for (register int i = 1; i <= n; i++) scanf( %lld , &a[i]), f1 += a[i];     int u, v;     scanf( %d , &m);     for (register int i = 1; i <= m; i++) {       scanf( %d%d , &u, &v);       add(u, v, -1);       add(v, u, 1);     }     if (f1 != 0) {       printf( Impossible n );       return 0;     }     memset(vis, 0, sizeof(vis));     a[1] += fr_dfs(1, 0);     h[1] = 1;     for (register int i = 1; i <= n; i++) {       if (!vis[i]) {         a[i] += fr_dfs(i, 0);         h[++tot] = i;       }     }     memset(vis, 0, sizeof(vis));     for (register int i = 1; i <= tot; i++) {       sc_dfs(h[i], 0, a[h[i]]);     }     for (register int i = 1; i <= n; i++) {       if (a[i]) {         printf( Impossible n );         return 0;       }     }     printf( Possible n );     for (register int i = 1; i <= m; i++) printf( %lld n , f[i]);     return 0;   }   