#include <bits/stdc++.h>
using namespace std;
const int maxn = 1E5 + 77;
struct REDGE {
  int x, y;
  long long v;
} redges[maxn];
struct EDGE {
  int to, next, idx;
} edges[maxn * 2];
int cEdge = 1, head[maxn];
void addEdge(int from, int to, int idx) {
  edges[cEdge] = (EDGE){to, head[from], idx};
  head[from] = cEdge++;
}
int N, M;
int C[maxn];
int ek;
long long sum[2];
int vis[maxn];
bool dfs1(int u, int d, int t) {
  if (vis[u]) {
    if (vis[u] != d) {
      ek = edges[t].idx;
      return false;
    } else {
      return true;
    }
  }
  vis[u] = d;
  sum[d - 1] += C[u];
  for (int k = head[u]; k; k = edges[k].next) {
    int v = edges[k].to;
    if (!dfs1(v, 3 - d, k)) return false;
  }
  return true;
}
bool bipart() { return dfs1(1, 1, 0); }
void dfs2(int u, int t) {
  long long suc = 0;
  vis[u] = 1;
  for (int k = head[u]; k; k = edges[k].next) {
    int v = edges[k].to;
    if (vis[v]) continue;
    dfs2(v, k);
    suc += redges[edges[k].idx].v;
  }
  if (t) redges[edges[t].idx].v = C[u] - suc;
}
int pk[maxn];
int vis3[maxn];
void dfs3(int u) {
  vis3[u] = true;
  for (int k = head[u]; k; k = edges[k].next) {
    int v = edges[k].to;
    if (vis3[v]) continue;
    if (!vis[v] || vis[v] == vis[u]) continue;
    pk[v] = edges[k].idx;
    dfs3(v);
  }
}
bool vis4[maxn];
void dfs4(int u) {
  long long suc = 0;
  vis4[u] = true;
  for (int k = head[u]; k; k = edges[k].next) {
    int v = edges[k].to;
    if (vis4[v]) continue;
    if (pk[v] && pk[v] != edges[k].idx) continue;
    pk[v] = edges[k].idx;
    dfs4(v);
    suc += redges[pk[v]].v;
  }
  if (pk[u]) redges[pk[u]].v = C[u] - suc;
}
int altro(int k, int v) {
  if (redges[k].x == v)
    return redges[k].y;
  else
    return redges[k].x;
}
void solveNoBipart() {
  int r = redges[ek].x;
  dfs3(r);
  dfs4(r);
  long long d = C[r];
  for (int k = head[r]; k; k = edges[k].next) {
    d -= redges[edges[k].idx].v;
  }
  d >>= 1;
  redges[ek].v = d;
  for (int u = redges[ek].y; u != r; u = altro(pk[u], u)) {
    d = -d;
    redges[pk[u]].v += d;
  }
}
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) {
    int x, y;
    scanf("%d%d", &x, &y);
    addEdge(x, y, i);
    addEdge(y, x, i);
    redges[i] = (REDGE){x, y};
  }
  if (bipart()) {
    if (sum[0] == sum[1]) {
      memset(vis, 0, sizeof(vis));
      dfs2(1, 0);
    } else {
      printf("NO\n");
      return 0;
    }
  } else {
    solveNoBipart();
  }
  printf("YES\n");
  for (int i = 1; i <= M; ++i) {
    cout << redges[i].v << endl;
  }
}
