//拓扑排序+优化一下

//author keyboarder

//time   2016/4/23 21:52

#include <iostream>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <algorithm>

#include <queue>

#include <math.h>

#include <queue>

#include <stack>

using namespace std;

#define INF 0x3f3f3f

#define pi acos(-1.0)

#define LL long long

#define mm 1000000007

#define N 1000010

struct asd{

    int to;

    int next;

};

asd q[N];

int head[N],tol;

int pre[N];

int out[N];

int val[N];

int dp[N];

int n,m;

void add(int a,int b)

{

    q[tol].to=b;

    q[tol].next=head[a];

    head[a]=tol++;

}

void tuopu()

{

    queue<int>e;

    while(!e.empty())

        e.pop();

    for(int i=1;i<=n;i++)

    {

        if(pre[i]==0)

        {

            pre[i]=-1;

            e.push(i);

        }

    }

    while(!e.empty())

    {

        int u=e.front();

        e.pop();

        for(int v=head[u];v!=-1;v=q[v].next)

        {

            int i=q[v].to;

            dp[i]=max(dp[u]+val[i],dp[i]);

            pre[i]--;

            if(pre[i]==0)

            {

                pre[i]=-1;

                e.push(i);

            }

        }

    }

}

int main()

{

    while(~scanf("%d%d",&n,&m))

    {

        for(int i=1;i<=n;i++)

        {

            scanf("%d",&val[i]);

        }

        int u,v;

        tol=0;

        memset(head,-1,sizeof(head));

        memset(pre,0,sizeof(pre));

        memset(out,0,sizeof(out));

        for(int i=0;i<m;i++)

        {

            scanf("%d%d",&u,&v);

            add(u,v);

            pre[v]++;

            out[u]++;

        }

        for(int i=1;i<=n;i++)

        {

            if(pre[i]==0)

            {

                dp[i]=val[i];

            }

            else

                dp[i]=-INF;

        }

        tuopu();

        int ans=-INF;

        for(int i=1;i<=n;i++)

        {

            if(out[i]==0)

                ans=max(ans,dp[i]);

        }

        printf("%d\n",ans);

    }

    return 0;

}