#include <bits/stdc++.h>
using namespace std;
struct edge {
  int to, next, id;
} e[100005 * 2];
int n, m, tot, idx, idy, ide;
int head[100005], c[100005], vis[100005];
long long a[100005], b[100005];
void add(int x, int y, int id) {
  e[++tot] = (edge){y, head[x], id};
  head[x] = tot;
}
bool pdfs(int x) {
  for (int i = head[x]; i; i = e[i].next)
    if (!c[e[i].to]) {
      c[e[i].to] = 3 - c[x];
      if (!pdfs(e[i].to)) return 0;
    } else if (c[e[i].to] == c[x]) {
      idx = x;
      idy = e[i].to;
      ide = i;
      return 0;
    }
  return 1;
}
long long dfs(int x) {
  vis[x] = 1;
  long long s = a[x];
  for (int i = head[x]; i; i = e[i].next)
    if (!vis[e[i].to]) {
      long long tmp = dfs(e[i].to);
      b[e[i].id] += tmp;
      s -= tmp;
    }
  return s;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%I64d", &a[i]);
  for (int i = 1; i <= m; i++) {
    int x, y;
    scanf("%d%d", &x, &y);
    add(x, y, i);
    add(y, x, i);
  }
  c[1] = 1;
  bool f = pdfs(1);
  if (f) {
    long long s = 0;
    for (int i = 1; i <= n; i++)
      if (c[i] == 1)
        s += a[i];
      else
        s -= a[i];
    if (s) return puts("NO"), 0;
    s = dfs(1);
    if (s) return puts("NO"), 0;
    puts("YES");
    for (int i = 1; i <= m; i++) printf("%I64d\n", b[i]);
    return 0;
  }
  long long s = dfs(1);
  if (s & 1) return puts("NO"), 0;
  s /= 2;
  if (c[idx] == 2) s = -s;
  memset(b, 0, sizeof(b));
  b[e[ide].id] = s;
  a[idx] -= s;
  a[idy] -= s;
  memset(vis, 0, sizeof(vis));
  s = dfs(1);
  if (s) return puts("NO"), 0;
  puts("YES");
  for (int i = 1; i <= m; i++) printf("%I64d\n", b[i]);
}
