#include <bits/stdc++.h>
using namespace std;
const int N = 3e5;
int n, m, head[N], cnt, dep[N], fa[N], pid[N];
long long c[N], val[N];
bool vis[N], use[N];
struct edge {
  int to, nxt, id;
} e[N << 1];
void finish() {
  cout << "YES\n";
  for (int i = 1; i <= m; ++i) cout << val[i] << '\n';
  exit(0);
}
void dfs(int u) {
  vis[u] = 1;
  for (int i = head[u]; i; i = e[i].nxt)
    if (!vis[e[i].to]) {
      fa[e[i].to] = u;
      dep[e[i].to] = dep[u] + 1;
      pid[e[i].to] = e[i].id;
      use[e[i].id] = 1;
      dfs(e[i].to);
    }
  if (u != 1) {
    val[pid[u]] = c[u];
    c[fa[u]] -= c[u];
    c[u] = 0;
  }
}
void dfs2(int u) {
  for (int i = head[u]; i; i = e[i].nxt)
    if (!use[e[i].id] && (dep[e[i].to] - dep[u]) % 2 == 0) {
      assert(dep[e[i].to] > dep[u]);
      int fh = dep[u] % 2;
      long long dlt = c[1] / 2;
      if (fh == 1) dlt *= -1;
      val[e[i].id] = dlt;
      c[u] -= dlt, c[e[i].to] -= dlt;
      for (int v = e[i].to; v != 1; v = fa[v]) {
        val[pid[v]] += c[v];
        c[fa[v]] -= c[v];
        c[v] = 0;
      }
      assert(!c[1]);
      finish();
    }
  for (int i = head[u]; i; i = e[i].nxt)
    if (use[e[i].id] && dep[e[i].to] > dep[u]) dfs2(e[i].to);
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= n; ++i) cin >> c[i];
  for (int i = 1; i <= m; ++i) {
    int u, v;
    cin >> u >> v;
    e[++cnt] = (edge){v, head[u], i}, head[u] = cnt;
    e[++cnt] = (edge){u, head[v], i}, head[v] = cnt;
  }
  dfs(1);
  if (c[1] % 2 == 0) {
    if (c[1])
      dfs2(1);
    else
      finish();
  }
  cout << "NO\n";
  return 0;
}
