#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;
}