dinic

#pragma comment(linker, "/STACK:256000000")
#define _CRT_SECURE_NO_WARNINGS
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<iostream>
#include<fstream>
#include<vector>
#include<string>
#include<map>
#include<set>
#include<queue>
#include<deque>
#include<bitset>
#include<sstream>
#include<unordered_set>
#include<unordered_map>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef pair<ll, ll> pii;
typedef pair<ll, pii> piii;
#define xx first
#define yy second.first
#define zz second.second
#define mp make_pair

const ll MOD = (ll)1e10 + 7;
const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };
const int MAXN = (int)1e6 + 5;
const int MAXH = 21;

struct edge
{
  int v, to;
  ll cap, fl;
  edge() {};
  edge(int v, int to, ll cap) : v(v), to(to), cap(cap), fl(0) {};
};

vector<edge> e(0);
vector<int> g[MAXN];
int used[MAXN];
ll d[MAXN];
ll s, t, n, m;
ll k;


bool bfs()
{
  queue<int> q;
  q.push(s);
  for (int i = 0; i < 2 * n + 2; i++)
    d[i] = MOD;
  d[s] = 0;
  while (!q.empty())
  {
    int v = q.front();
    q.pop();
    for (int i = 0; i < g[v].size(); i++)
    {
      int ei = g[v][i];
      int to = e[ei].to;
      ll cap = e[ei].cap - e[ei].fl;
      if (d[to] > d[v] + 1 && cap > 0)
      {
        d[to] = d[v] + 1;
        q.push(to);
      }
    }
  }
  return (d[t] < MOD);
}

ll dfs(int v, ll flow)
{
  if (v == t)
    return flow;
  for (; used[v] < g[v].size(); used[v]++)
  {
    int ei = g[v][used[v]], to = e[ei].to;
    ll cap = e[ei].cap - e[ei].fl;
    if (cap > 0 && d[to] == d[v] + 1)
    {
      ll mfl = min(cap, flow);
      mfl = dfs(to, mfl);
      if (mfl > 0)
      {
        e[ei].fl += mfl;
        e[ei ^ 1].fl -= mfl;
        return mfl;
      }
    }
  }
  return 0ll;
}

ll cnt[MAXN];

int main()
{
  ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifdef _DEBUG
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
  cin >> k >> n >> m >> s >> t;
  s--, t--;
  if (s == t)
  {
    cout << "NO";
    return 0;
  }
  for (int i = 0; i < n; i++)
    cin >> cnt[i];
  for (int i = 0; i < m; i++)
  {
    int v, to;
    cin >> v >> to;
    v--, to--;
    if (to != s || v != t)
    {
      g[2 * v + 1].push_back(e.size());
      e.push_back(edge(2 * v + 1, 2 * to, MOD));
      g[2 * to].push_back(e.size());
      e.push_back(edge(2 * to, 2 * v + 1, 0));
    }
    if (to != t || v != s)
    {
      g[2 * to + 1].push_back(e.size());
      e.push_back(edge(2 * to + 1, 2 * v, MOD));
      g[2 * v].push_back(e.size());
      e.push_back(edge(2 * v, 2 * to + 1, 0));
    }
  }
  for (int i = 0; i < n; i++)
  {
    if (i == s || i == t)
      continue;
    g[2 * i].push_back(e.size());
    e.push_back(edge(2 * i, 2 * i + 1, cnt[i]));
    g[2 * i + 1].push_back(e.size());
    e.push_back(edge(2 * i + 1, 2 * i, 0));
  }
  s = s * 2 + 1;
  t = t * 2;

  ll ans = 0;
  while (bfs())
  {
    for (int i = 0; i < 2 * n; i++)
      used[i] = 0;
    ll fl = 0;
    while (fl = dfs(s, MOD))
    {
      ans += fl;
    }
  }
  if (ans > k)
    cout << "NO";
  else
    cout << "YES";
}