#include <fstream>
#include <vector>
using namespace std;

ifstream in("asmax.in");
ofstream out("asmax.out");

const int N=16001;
vector <int> v[N];
int val[N], n, sum[N];
bool viz[N], vf[N];

void dfs(int x)
{
    viz[x]=true;
    sum[x]=val[x];
    for(int i=0;i<v[x].size();i++)
        if(!viz[v[x][i]])
        {
            dfs(v[x][i]);
            if(sum[v[x][i]]>0)
                sum[x]+=sum[v[x][i]];
        }
}

int main()
{
    int iTemp1, iTemp2, vmax=-1000000000;

    in>>n;
    for(int i=1;i<=n;i++)
        in>>val[i];
    for(int i=0;i<n;i++)
    {
        in>>iTemp1>>iTemp2;
        v[iTemp1].push_back(iTemp2);
        vf[iTemp2]=1;
    }

    for(int i=1;i<=n;i++)
        if(vf[i]==0)
        {
            dfs(i);
            break;
        }

     for(int i=1;i<=n;i++)
     {
         if(sum[i]>vmax)
            vmax=sum[i];
     }


     out<<vmax;

     in.close();
     out.close();
}