#include <bits/stdc++.h>
//#include <atcoder/modint>
//#include <atcoder/math>
//#include <boost/multiprecision/cpp_int.hpp>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
#pragma GCC optimize("O3")
#define REP(i, n) for(int i = 0; i < n; i++)
#define REPP(i, n) for(int i = 1; i <= n; i++)
#define ALL(obj) (obj).begin(), (obj).end()
#define EPS (1e-9)
#define INF (1e17)
#define PI (acos(-1))
//const double PI = acos(-1);
//const double EPS = 1e-15;
//long long INF=(long long)1E17;
#define i_7 (long long)(1e9+7)
//#define i_7 998'244'353
long mod(long a){
    long long c = a % i_7;
    if(c >= 0) return c;
    return c + i_7;
}
long long po(long a, long b){
    if(b == 0) return 1;
    
    long long z = po(a , b / 2);
    z = mod(z * z);
    if(b % 2 != 0) z = mod(a * z);
    return z;
}
 
bool prime_(int n){
  if(n == 1){
    return false;
  }else if(n == 2){
    return true;
  }else{
    for(int i = 2; i <= std::sqrt(n); i++) if(n % i == 0) return false;
    return true;
  }
}
 
long long gcd_(long long a, long long b){
  if(a < b) std::swap(a,b);
  if(a % b == 0) return b;
  else return gcd_(b, a % b);
}
 
long long lcm_(long long x, long long y){
  return (x / gcd_(x,y)) * y;
}
 
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//using mint = modint998244353;
//using namespace boost::multiprecision;
//using namespace __gnu_pbds;   

vector<int> a;
vector<vector<int>> G;
vector<int> dp;
const int limit = -(1e9 + 100);
int dfs(int v){
  if(dp[v] != limit) return dp[v];
  int res = limit;
  for(int nv: G[v]){
    res = max(res, a[nv]);
    res = max(res, dfs(nv));
  }
  return dp[v] = res;
}
 
int main(){
  //using namespace std;
  int n, m;
  cin>>n>>m;
  a.resize(n);
  REP(i, n) cin>>a[i];
  G.resize(n);
  int x[m], y[m];
  REP(i, m){
    cin>>x[i]>>y[i];
    x[i]--; y[i]--;
  }
  
  REP(i, m) G[x[i]].push_back(y[i]);
  dp.resize(n, limit);
  int ans = limit;
  for(int i = n - 1; i >= 0; i--){
    int temp = dfs(i) - a[i];
    ans = max(ans, temp);
  }
  cout << ans << endl;
  return 0;
}
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int N = 2e5+2;
int nums1[N];
int nums[N]; //进入i的最小值
bool vis[N];
int n,m,x,y;

int main()
{
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        cin>>nums1[i];
        nums[i] = 1e9;
    }
    vector<pair<int,int>> vp;
    for(int i=0;i<m;i++){
        cin>>x>>y;
        vp.emplace_back(make_pair(x,y));
    }
    sort(vp.begin(),vp.end());
    for(int i=0;i<m;i++){
        int st = vp[i].first;
        int end = vp[i].second;
        nums[end] = min(nums[end],min(nums[st],nums1[st]));
        vis[end] = 1;
        //cout<<st<<" "<<end<<" "<<nums[end]<<endl;
    }

    int res = -1e9;
    for(int i=1;i<=n;i++){
        //cout<<i<<" "<<nums1[i]-nums[i]<<" "<<vis[i]<<endl;
        if(vis[i])
        {   
            res = max(res,nums1[i]-nums[i]);
        }
    }
    
    cout<<res<<endl;
    return 0;
}


