#include<iostream>
#include<cstring>
#include<algorithm> 
#include<queue>
using namespace std;
const int N=2e5+10;
int h[N],e[N],ne[N],idx;
int hs[N],es[N],nes[N],idxs;
int timestamp,low[N],dfn[N];
int stk[N],top;
int instk[N];
int scc_cnt,id[N],Size[N];
int din[N],dist[N],w[N];
int n,m;
void add(int a,int b){
	e[idx]=b,ne[idx]=h[a],h[a]=idx++;
}
void addscc(int a,int b){
	es[idx]=b,nes[idx]=hs[a],hs[a]=idxs++;
}
void tarjan(int u){
    dfn[u]=low[u]=++timestamp;
    stk[++top]=u,instk[u]=true;
    for(int i=h[u];~i;i=ne[i]){
        int j=e[i];
        if(!dfn[j]){
            tarjan(j);
            low[u]=min(low[u],low[j]);
        }
        else if(instk[j])low[u]=min(low[u],dfn[j]);
    }
    if(dfn[u]==low[u]){
        ++scc_cnt;
        int y;
        do{
            y=stk[top--];
            instk[y]=false;
            id[y]=scc_cnt;
            Size[scc_cnt]+=w[y];
        }while(y!=u);
    }
}
int topo(){
	queue<int>q;
	//memset(dist,0x3f,sizeof dist);
	for(int i=1;i<=scc_cnt;i++){
		if(!din[i])q.push(i),dist[i]=w[i];
	}
	while(q.size()){
		int ver=q.front();
		q.pop();
		for(int i=hs[ver];~i;i=nes[i]){
			int j=es[i];
			dist[j]=min(dist[j],dist[ver]+w[i]);
			if(!(--din[j]))q.push(j);
		}
	}
	int maxn=-1;
	for(int i=1;i<=scc_cnt;i++)maxn=max(maxn,dist[i]);
	return maxn;
}
int main(){
	memset(h,-1,sizeof h);
	memset(hs,-1,sizeof hs);
	cin>>n>>m;
	for(int i=1;i<=n;i++)cin>>w[i];
	while(m--){
		int a,b;
		cin>>a>>b;
		add(a,b);
	}
	for(int i=1;i<=n;i++)
		if(!dfn[i])tarjan(i);
	for(int i=1;i<=n;i++){
		for(int j=h[i];~j;j=ne[j]){
			int k=e[j];
			int a=id[i],b=id[k];
			if(a!=b)addscc(a,b),din[b]++;
		}
	}
	cout<<topo();
    return 0;
}