#include<stdio.h>
#include<string.h>
#define maxn 100005
int n,m;
int v[maxn];
struct node
{int vex;
 node * next;
};
node * side[maxn];

int que[maxn];
int ind[maxn];
int outd[maxn];
int res[maxn];
int mark[maxn];

int max(int a,int b)
{return a>b?a:b;
}
void bfs()
{
	int closed=-1,open=-1;
	memset(mark,0,sizeof(mark));
	int i,j;
	for(j=1;j<=n;j++)
		res[j]=v[j];

	for(i=1;i<=n;i++)
		if(outd[i]==0){
			closed++;
			que[closed]=i;
			mark[i]=1;
		}
	while(open<closed)
	{
		open++;
		j=que[open];
		node *p=side[j];
		while(p!=NULL)
		{
			i=p->vex;
			res[i]=max(res[i],res[j]+v[i]);
			if(!mark[i]){
				closed++;
				que[closed]=i;
				mark[i]=1;
			}
			p=p->next;
		}
	}
}

int main()
{
	//freopen("file.in","r",stdin);

	int i,j,k;

	while(scanf("%d%d",&n,&m)!=EOF)
	{
		for(i=1;i<=n;i++){
			scanf("%d",&v[i]);
		}
		memset(ind,0,sizeof(ind));
		memset(outd,0,sizeof(outd));
		for(i=1;i<=n;i++) {
			side[i]=NULL;
		}
		for(k=0;k<m;k++)
		{
			scanf("%d%d",&i,&j);
			ind[j]++;
			outd[i]++;
			node *q;
			q=new node;
			q->vex=i;
			q->next=side[j];
			side[j]=q;
		}

		int best=-0x7fffffff;
		bfs();
		for(k=1;k<=n;k++)
			if(ind[k]==0){
				best=max(best,res[k]);
			}
		printf("%d\n",best);
	}
   return 0;
}

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