#include <bits/stdc++.h>
using namespace std;
inline void read(int &x) {
  int v = 0, f = 1;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = (c & 15);
  while (isdigit(c = getchar())) v = (v << 1) + (v << 3) + (c & 15);
  x = v * f;
}
inline void read(long long &x) {
  long long v = 0ll, f = 1ll;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = (c & 15);
  while (isdigit(c = getchar())) v = (v << 1) + (v << 3) + (c & 15);
  x = v * f;
}
inline void readc(char &x) {
  char c;
  while (((c = getchar()) == ' ') || c == '\n')
    ;
  x = c;
}
int n, m, i, j, vis[100005], ve[100005], dep[100005];
long long a[100005], px[100005], py[100005], res[100005];
vector<int> e[100005];
void dfs1(int x) {
  vis[x] = 1;
  for (__typeof((e[x]).begin()) it = (e[x]).begin(); it != (e[x]).end(); it++) {
    if (!ve[*it]) {
      int y = px[*it] ^ py[*it] ^ x;
      if (!vis[y]) {
        ve[*it] = 1;
        dep[y] = dep[x] + 1;
        dfs1(y);
        res[*it] += a[y];
        a[x] -= a[y];
        a[y] = 0;
      }
    }
  }
}
int main() {
  read(n);
  read(m);
  for (((i)) = (1); ((i)) <= ((n)); ((i))++) read(a[i]);
  for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
    int x, y;
    read(x);
    read(y);
    px[i] = x;
    py[i] = y;
    e[x].push_back(i);
    e[y].push_back(i);
  }
  dfs1(1);
  for (((i)) = (1); ((i)) <= ((m)); ((i))++)
    if (!ve[i]) {
      if (!((dep[px[i]] ^ dep[py[i]]) & 1)) {
        if (dep[px[i]] & 1)
          res[i] -= a[1] / 2;
        else
          res[i] = +a[1] / 2;
        a[px[i]] -= res[i];
        a[py[i]] -= res[i];
        break;
      }
    }
  memset(vis, 0, sizeof(vis));
  memset(ve, 0, sizeof(ve));
  dfs1(1);
  if (a[1]) {
    puts("NO");
    return 0;
  }
  puts("YES");
  for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
    printf("%lld\n", res[i]);
  }
  return 0;
}
