#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 10;
long long n, m, from[MAXN], to[MAXN], w[MAXN], sum[MAXN];
vector<int> adj[MAXN];
int col[MAXN];
int root = -1;
int sec[MAXN], sz;
int tv = -1;
void dfs(int v, int c = 1, int p = -1) {
  if (col[v]) {
    if (col[v] != c) {
      root = v;
      sec[sz++] = p;
      tv = v;
    }
    return;
  }
  col[v] = c;
  for (int e : adj[v]) {
    int u = from[e] ^ to[e] ^ v;
    dfs(u, 3 - c, e);
    if (root != -1) {
      if (v == tv) tv = -1;
      if (tv != -1) sec[sz++] = p;
      return;
    }
  }
}
int par[MAXN], q[MAXN], h, t, cnt[MAXN];
void dfs2(int v, int p = -1) {
  col[v] = 1;
  par[v] = p;
  for (int e : adj[v])
    if (e ^ p) {
      int u = from[e] ^ to[e] ^ v;
      if (!col[u]) {
        dfs2(u, e);
        cnt[v]++;
      }
    }
  if (!cnt[v]) q[t++] = v;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m;
  for (int i = 0; i < n; i++) cin >> sum[i];
  for (int i = 0; i < m; i++) {
    cin >> from[i] >> to[i], from[i]--, to[i]--;
    adj[from[i]].push_back(i);
    adj[to[i]].push_back(i);
    w[i] = 1;
    sum[from[i]] -= 1;
    sum[to[i]] -= 1;
  }
  dfs(0);
  if (root == -1) root = 0;
  memset(col, 0, sizeof(col));
  dfs2(root);
  while (t - h) {
    int v = q[h++];
    if (v == root) break;
    w[par[v]] += sum[v];
    int p = from[par[v]] ^ to[par[v]] ^ v;
    sum[p] -= sum[v];
    sum[v] = 0;
    cnt[p]--;
    if (cnt[p] == 0) q[t++] = p;
  }
  if (sum[root] == 0) {
    cout << "YES\n";
    for (int i = 0; i < m; i++) cout << w[i] << "\n";
  } else {
    if (sz == 0)
      cout << "NO\n";
    else {
      assert((sum[root] & 1) == 0);
      for (int i = 0; i < sz; i++)
        w[sec[i]] += (i & 1 ? -sum[root] / 2 : sum[root] / 2);
      cout << "YES\n";
      for (int i = 0; i < m; i++) cout << w[i] << "\n";
    }
  }
  return 0;
}
