#include <bits/stdc++.h>
using namespace std;
const int MAX = 112345;
struct Edge {
  int v, nxt;
} edge[MAX << 2];
int head[MAX], etot;
void add_edge(int u, int v) {
  edge[etot] = (Edge){v, head[u]};
  head[u] = etot++;
}
int dep[MAX], f[MAX], A[MAX], eid = -1, x, y;
bool vis[MAX];
long long cost[MAX], from[MAX];
long long dfs(int u, int fa) {
  vis[u] = true;
  dep[u] = dep[fa] + 1;
  f[u] = fa;
  long long sum = 0;
  for (int i = head[u]; ~i; i = edge[i].nxt) {
    int v = edge[i].v;
    if (vis[v] && dep[v] < dep[u] && (dep[u] - dep[v]) % 2 == 0) {
      eid = i;
      x = v, y = u;
    }
    if (vis[v]) continue;
    from[v] = i >> 1;
    dfs(v, u);
    sum += cost[i >> 1];
  }
  if (from[u] != -1) cost[from[u]] = A[u] - sum;
  return A[u] - sum;
}
int n, m;
void out() {
  printf("YES\n");
  for (int i = 0; i < m; i++) {
    printf("%lld\n", cost[i]);
  }
}
int main() {
  memset(from, -1, sizeof(from));
  memset(head, -1, sizeof(head));
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d", A + i);
  for (int i = 1; i <= m; i++) {
    int u, v;
    scanf("%d %d", &u, &v);
    add_edge(u, v);
    add_edge(v, u);
  }
  long long remain = dfs(1, 0);
  if (remain == 0) {
    out();
    return 0;
  }
  if (remain % 2 || eid == -1) {
    printf("NO\n");
    return 0;
  }
  cost[eid / 2] = remain / 2;
  ;
  if (dep[x] % 2 == 0) cost[eid / 2] *= -1;
  while (dep[y] > dep[x]) {
    cost[from[y]] += ((dep[y] - 1) % 2 ? 1 : -1) * remain / 2;
    y = f[y];
  }
  while (x > 1) {
    cost[from[x]] += ((dep[x] - 1) % 2 ? 1 : -1) * remain;
    x = f[x];
  }
  out();
}
