#include <cstdio>

#include <iostream>

#include <cstring>

#include <cstdlib>

#include <cmath>

#include <vector>

#include <queue>

#include <stack>

#include <map>

#include <algorithm>

#include <set>

using namespace std;

typedef long long ll;

typedef unsigned long long Ull;

#define MM(a,b) memset(a,b,sizeof(a));

const double eps = 1e-10;

const int  inf =0x7f7f7f7f;

const double pi=acos(-1);

const int maxn=40000;

int n,x,y,a[6005],dp[6005][3],indeg[6005];

vector<int> G[6005];

int solve()

{

    int ans=0;

    queue<int> q;

    for(int i=1;i<=n;i++)

      {

          ans=max(ans,a[i]);

          dp[i][1]=a[i];

          dp[i][0]=0;

          if(!indeg[i])  {q.push(i);}

      }

    while(q.size())

    {

      int u=q.front();q.pop();

      for(int i=0;i<G[u].size();i++)

      {

          int v=G[u][i];

          dp[v][0]+=max(dp[u][0],dp[u][1]);

          dp[v][1]+=dp[u][0];

          indeg[v]--;

          if(!indeg[v]) q.push(v);

          ans=max(ans,max(dp[v][0],dp[v][1]));

      }

    }

    return ans;

}

int main()

{

    while(~scanf("%d",&n))

    {

        for(int i=1;i<=n;i++) {G[i].clear();scanf("%d",&a[i]);}

        MM(indeg,0);

        for(;;)

        {

            scanf("%d %d",&x,&y);

            if(!x&&!y) break;

            G[x].push_back(y);

            indeg[y]++;

        }

        printf("%d\n",solve());

    }

    return 0;

}