#include<bits/stdc++.h>
using namespace std ;

#define FASTIO ios::sync_with_stdio(0) ; cin.tie(0) ; cout.tie(0) ;
#define int long long
#define mod ((int)1e9 + 7)

int n , m , ans = INT_MIN ;
vector<int> a , mb , ms ;
vector<vector<int>> adj ;
vector<bool> visited ;

void dfs(int x){
        visited[x] = true ;
        for(int y : adj[x]){
                if(!visited[y]) dfs(y) ;
                ms[x] = max(max(ms[x] , ms[y]) , mb[y]) ;
        }
}

void solve(){
        cin >> n >> m ;
        a.resize(n + 1) ; mb.resize(n + 1) ;
        ms.resize(n + 1 , 0) ; visited.resize(n + 1 , false) ;
        adj.resize(n + 1 , vector<int>()) ;
        for(int i = 1 ; i <= n ; ++i){ cin >> a[i] ; mb[i] = a[i] ; }
        for(int i = 0 ; i < m ; ++i){
                int x , y ; cin >> x >> y ;
                adj[x].push_back(y) ;
        }
        for(int i = 1 ; i <= n ; ++i){
                if(visited[i]) continue ;
                dfs(i) ;
        }
        for(int i = 1 ; i <= n ; ++i){
                if(ms[i] == 0) continue ;
                //cout << ms[i] << " " << mb[i] << "\n" ;
                ans = max(ans , ms[i] - mb[i]) ;
        }
        cout << ans << "\n" ;
}

signed main(){
        FASTIO
        int T = 1 ; 
       // cin >> T ;
        while(T--) solve() ;
        return 0 ;
}
#include<bits/stdc++.h>
#include<iostream>
#include<string>
#include<cmath>
#include<cstdio>
#include<cctype>
#include<cstring>
#include<iomanip>
#include<cstdlib>
#include<ctime>
#include<set>
#include<map>
#include<utility>
#include<queue>
#include<vector>
#include<stack>
#include<sstream>
#include<algorithm>
#define forn(i,a,b)for(int i=(a),_b=(b);i<=_b;i++)
#define fore(i,b,a)for(int i=(b),_a=(a);i>=_a;i--)
#define rep(i,n)for(int i=0,_n=n;i<n;i++)
#define ll long long
#define pii pair<int,int>
#define vi vector<int>
#define vpii vector<pii>
#define m_p make_pair
#define re return
#define pb push_back
#define si set<int>
#define ld long double
#define X first
#define Y second
#define st string
#define ull unsigned long long
#define mod 1000000007
#define INF 1000000007
#define x1 XZVJDFADSPFOE
#define y1 GASDIJSLDAEJF
#define x2 DFDAJKVOHKWIW
#define y2 PSFSAODSXVNMQ
#define LLINF 0x3f3f3f3f3f3f3f3fLL
#define foreach(i,c) for(__typeof(c.begin())i=(c.begin());i!=(c).end();i++)
using namespace std;
inline void read(int &x)
{
	short negative=1;
    x=0;
    char c=getchar();
    while(c<'0' || c>'9')
    {
		if(c=='-')
			negative=-1;
		c=getchar();
	}
    while(c>='0' && c<='9')
        x=(x<<3)+(x<<1)+(c^48),c=getchar();
    x*=negative;
}
ll quickpower(ll n,ll k){
	ll ans=1;
	while(k){
		if(k%2){
			ans*=n;
			ans%=mod;
		}
		n*=n;
		n%=mod;
		k/=2;
	}
	return ans;
}
string int_to_string(int n)
{
	string s="";
	while(n)
	{
		int now=n%10;
		s+=now+'0';
		n/=10;
	}
	reverse(s.begin(),s.end());
	return s;
}
int string_to_int(string s)
{
	int n=0;
	rep(i,s.size())
	{
		n*=10;
		n+=s[i]-'0';
	}
	return n;
}
int n,m;
vector<int>v[200100];
ll a[200100];
bool used[200100];
ll can[200100];
void dfs(int u)
{
	used[u]=1;
	rep(i,v[u].size())
	{
		if(!used[v[u][i]])dfs(v[u][i]);
		can[u]=max(can[u],can[v[u][i]]);
		can[u]=max(can[u],a[v[u][i]]);
	}
}
int main()
{
	ios::sync_with_stdio(0);
	cin>>n>>m;
	rep(i,n)cin>>a[i];
	rep(i,m)
	{
		int x,y;
		cin>>x>>y;
		x--;
		y--;
		v[x].pb(y);
	}
	rep(i,n)can[i]=-1e18;
	fore(i,n-1,0)
	{
		if(!used[i])dfs(i);
	}
	ll ans=-1e18;
	rep(i,n)
	{
		ans=max(ans,can[i]-a[i]);
	}
	cout<<ans<<endl;
	return 0;
}
