#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
struct edge {
  int to, nxt;
  long long w;
} e[N << 1];
int head[N], tot = 1;
int n, m, vis[N];
long long s[3], a[N], d[N];
void adde(int u, int v) {
  e[++tot] = edge{v, head[u]};
  head[u] = tot;
  return;
}
void Dfs(int u, int fa) {
  vis[u] = 3 - vis[fa];
  s[vis[u]] += a[u];
  for (int i = head[u]; i; i = e[i].nxt) {
    int v = e[i].to;
    if (v == fa || vis[v]) continue;
    Dfs(v, u);
  }
  return;
}
void dfs(int u, int fa) {
  vis[u] = 1;
  for (int i = head[u]; i; i = e[i].nxt) {
    int v = e[i].to;
    if (v == fa || vis[v]) continue;
    dfs(v, u);
    e[i].w = a[v], e[i ^ 1].w = a[v];
    a[u] -= a[v], a[v] = 0;
  }
  return;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%lld", &a[i]);
  int u, v;
  for (int i = 1; i <= m; i++) {
    scanf("%d%d", &u, &v);
    adde(u, v), adde(v, u);
  }
  vis[0] = 1;
  Dfs(1, 0);
  int id = -1;
  for (int u = 1; u <= n; u++) {
    for (int i = head[u]; i; i = e[i].nxt) {
      int v = e[i].to;
      if (vis[u] == vis[v]) {
        id = i;
        break;
      }
    }
    if (id != -1) break;
  }
  if (s[1] != s[2]) {
    if (id == -1) return printf("NO\n"), 0;
    u = e[id].to, v = e[id ^ 1].to;
    long long d = s[3 - vis[u]] - s[vis[u]];
    if (d % 2 != 0) return printf("NO\n"), 0;
    a[u] += d / 2, a[v] += d / 2;
    e[id].w = -d / 2, e[id ^ 1].w = -d / 2;
  }
  printf("YES\n");
  memset(vis, 0, sizeof(vis));
  dfs(1, 0);
  for (int i = 2; i <= tot; i += 2) printf("%lld\n", e[i].w);
  return 0;
}
