#include <bits/stdc++.h>
using namespace std;
int n, m;
int c[100010];
int x[100010], y[100010];
vector<int> t[100010];
int f[100010];
int find(int x) { return (f[x] == -1 ? x : f[x] = find(f[x])); }
int fa[100010], dep[100010];
int dfn[100010], rnk[100010], totn = 0;
int siz[100010], son[100010], top[100010];
void dfs1(int k) {
  dep[k] = dep[fa[k]] + 1;
  siz[k] = 1;
  for (vector<int>::iterator it = t[k].begin(); it != t[k].end(); ++it) {
    if (*it == fa[k]) continue;
    fa[*it] = k;
    dfs1(*it);
    siz[k] += siz[*it];
    if (son[k] == 0 || siz[*it] > siz[son[k]]) son[k] = *it;
  }
  return;
}
void dfs2(int k, int tp) {
  dfn[k] = ++totn;
  rnk[totn] = k;
  top[k] = tp;
  if (son[k]) dfs2(son[k], tp);
  for (vector<int>::iterator it = t[k].begin(); it != t[k].end(); ++it) {
    if (*it == fa[k] || *it == son[k]) continue;
    dfs2(*it, *it);
  }
  return;
}
int LCA(int a, int b) {
  while (top[a] != top[b]) {
    if (dep[top[a]] < dep[top[b]]) swap(a, b);
    a = fa[top[a]];
  }
  return (dep[a] < dep[b] ? a : b);
}
long long v[100010];
void dfs3(int k) {
  v[k] = c[k];
  for (vector<int>::iterator it = t[k].begin(); it != t[k].end(); ++it) {
    if (*it == fa[k]) continue;
    dfs3(*it);
    v[k] -= v[*it];
  }
  return;
}
long long ve[100010];
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; ++i) scanf("%d", &c[i]);
  for (int i = 1; i <= m; ++i) scanf("%d%d", &x[i], &y[i]);
  memset(f, -1, sizeof(f));
  for (int i = 1; i <= m; ++i) {
    int p = find(x[i]), q = find(y[i]);
    if (p == q) continue;
    f[p] = q;
    t[x[i]].push_back(y[i]);
    t[y[i]].push_back(x[i]);
  }
  dfs1(1);
  dfs2(1, 1);
  dfs3(1);
  for (int i = 1; i <= m; ++i) {
    if (fa[x[i]] == y[i] || fa[y[i]] == x[i]) continue;
    if ((dep[x[i]] + dep[y[i]] - 2 * dep[LCA(x[i], y[i])]) % 2 == 0) {
      int val = v[1] / 2;
      val = val * (dep[x[i]] % 2 == 0 ? -1 : 1);
      ve[i] = val;
      c[x[i]] -= val;
      c[y[i]] -= val;
      break;
    }
  }
  dfs3(1);
  if (v[1] != 0) {
    puts("NO");
    return 0;
  }
  puts("YES");
  for (int i = 1; i <= m; ++i) {
    if (fa[x[i]] == y[i] || fa[y[i]] == x[i]) {
      if (dep[x[i]] < dep[y[i]]) swap(x[i], y[i]);
      ve[i] = v[x[i]];
    }
    printf("%lld\n", ve[i]);
  }
  return 0;
}
