#include <bits/stdc++.h>
using namespace std;
int read() {
  char c = getchar();
  int x = 0, f = 1;
  while (c < '0' || c > '9') f = (c == '-') ? -1 : f, c = getchar();
  while (c >= '0' && c <= '9') x = x * 10 + c - 48, c = getchar();
  return x * f;
}
const int N = 1e5 + 10;
struct Edge {
  int nxt, point;
} edge[N << 1];
int tot = 1, head[N];
int dep[N];
pair<int, int> e[N];
long long f[N], w[N], c[N], now[N];
int Id[N << 1];
bool used[N];
void add_edge(int u, int v) {
  edge[++tot].nxt = head[u];
  edge[tot].point = v;
  head[u] = tot;
}
void dfs(int u, int fa) {
  dep[u] = dep[fa] + 1;
  used[u] = 1;
  for (int i = head[u]; i; i = edge[i].nxt) {
    int v = edge[i].point;
    if (used[v]) continue;
    dfs(v, u);
    f[Id[i]] = c[v] - now[v];
    now[u] += f[Id[i]];
  }
}
void calc(int u) {
  used[u] = 1;
  for (int i = head[u]; i; i = edge[i].nxt) {
    int v = edge[i].point;
    if (used[v]) continue;
    calc(v);
    f[Id[i]] = c[v] - now[v];
    now[u] += f[Id[i]];
  }
}
int main() {
  int n = read(), m = read();
  long long mx = 2ll * n * n;
  for (int i = 1; i <= n; ++i) c[i] = read();
  for (int i = 1; i <= m; ++i) {
    int u = read(), v = read();
    e[i] = make_pair(u, v);
    add_edge(u, v);
    add_edge(v, u);
    Id[tot] = Id[tot ^ 1] = i;
  }
  dfs(1, 0);
  if (now[1] == c[1]) {
    for (int i = 1; i <= m; ++i) {
      if (-mx <= f[i] && mx >= f[i]) continue;
      puts("NO");
      return 0;
    }
    puts("YES");
    for (int i = 1; i <= m; ++i) printf("%lld\n", f[i]);
  } else {
    if ((c[1] - now[1]) & 1) return puts("NO"), 0;
    for (int i = 1; i <= m; ++i) {
      int u = e[i].first, v = e[i].second;
      if (abs(dep[u] - dep[v]) & 1)
        continue;
      else {
        long long x = ((c[1] - now[1]) / 2);
        if (abs(dep[u] - dep[1]) & 1) x = -x;
        memset(now, 0, sizeof(now));
        memset(f, 0, sizeof(f));
        memset(used, 0, sizeof(used));
        f[i] = x;
        now[u] = x, now[v] = x;
        calc(1);
        assert(c[1] == now[1]);
        for (int i = 1; i <= m; ++i) {
          if (-mx <= f[i] && mx >= f[i]) continue;
          return puts("NO"), 0;
        }
        puts("YES");
        for (int i = 1; i <= m; ++i) printf("%lld\n", f[i]);
        return 0;
      }
    }
    puts("NO");
  }
  return 0;
}
