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//Przemysław Jakub Kozłowski
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <cassert>
#include <sys/time.h>
#include <iomanip>
#define FI first
#define SE second
#define MP make_pair
using namespace std;
typedef long long LL;

namespace LCABin
{
    namespace Oblicz_glebokosci
    {
        const int *ojc;
        int *glb;
        void DFS(int x)
        {
            if(!glb[ojc[x]] && ojc[x] != 0) DFS(ojc[x]);
            glb[x] = glb[ojc[x]]+1;
        }
        void main(int n, const int *f_ojc, int *f_glb)
        {ojc = f_ojc;glb = f_glb;
            for(int i = 0;i <= n;i++) glb[i] = 0;
            for(int i = 1;i <= n;i++)
                if(!glb[i])
                    DFS(i);
        }
    };
    struct Main
    {
        int k;
        int **przodek;
        int *glebokosc;
        Main(int n, const int *ojc) // n - liczba wierzchołków (numery od 1 do n), ojc - tablica ojców, ojc[korzen] = 0, ojciec[korzen] != korzen
        {
            k = 0;
            while((1<<(k+1)) <= n) k++; // k = floor(log(n))

            przodek = new int*[k+1];
            for(int i = 0;i <= k;i++)
                przodek[i] = new int[n+1];
            glebokosc = new int[n+1];

            Oblicz_glebokosci::main(n, ojc, glebokosc);

            przodek[0][0] = 0;
            for(int i = 1;i <= n;i++)
                przodek[0][i] = ojc[i];
            for(int p = 1;p <= k;p++)
                for(int i = 0;i <= n;i++)
                    przodek[p][i] = przodek[p-1][przodek[p-1][i]];
        }
        ~Main()
        {
            for(int i = 0;i <= k;i++)
                delete [] przodek[i];
            delete [] przodek;
            delete [] glebokosc;
        }

        int query(int a, int b)
        {
            if(glebokosc[a] > glebokosc[b]) swap(a,b);
            for(int p = k;glebokosc[a] < glebokosc[b];p--)
                if(glebokosc[a] <= glebokosc[przodek[p][b]])
                    b = przodek[p][b];
            for(int p = k;p >= 0;p--)
                if(przodek[p][a] != przodek[p][b])
                {
                    a = przodek[p][a];
                    b = przodek[p][b];
                }
            if(a != b)
            {
                a = przodek[0][a];
                b = przodek[0][b];
            }
            return a;
        }
    };
};

namespace Oblicz
{
    void DFS(int x);

    pair<int,int> *dlar;

    vector<int> *syn;
    vector<int> *KR;
    int *obecnysyn;

    vector<int> *KUB;
    vector<int> *RUB;

    LL main(int n, int k, int *gram, int *ojc, pair<int,int> *reakcje)
    {
        /*cerr << "N: " << n << " K: " << k << endl;
        cerr << "Gram: ";
        for(int i = 1;i <= n;i++)
            cerr << gram[i] << " ";
        cerr << endl;
        cerr << "Ojc: ";
        for(int i = 1;i <= n;i++)
            cerr << ojc[i] << " ";
        cerr << endl;
        cerr << "Reakcje: ";
        for(int i = 1;i <= k;i++)
            cerr << "(" << reakcje[i].FI << "," << reakcje[i].SE <<") ";
        cerr << endl;*/

        dlar = new pair<int,int>[k+7];
        LCABin::Main *lca = new LCABin::Main(n, ojc);
        for(int i = 1;i <= k;i++)
            dlar[i].SE = lca->query(reakcje[i].FI, reakcje[i].SE);
        delete lca;

        syn = new vector<int>[n+7];
        KR = new vector<int>[n+7];
        obecnysyn = new int[n+7];
        for(int i = 1;i <= n;i++)
            syn[ojc[i]].push_back(i);
        for(int i = 1;i <= k;i++)
            KR[reakcje[i].SE].push_back(i);
        DFS(0);
        delete [] obecnysyn;
        delete [] KR;
        delete [] syn;

        KUB = new vector<int>[n+7];
        RUB = new vector<int>[n+7];
        for(int i = 1;i <= k;i++)
            KUB[dlar[i].FI].push_back(i);
        for(int i = 1;i <= n;i++)
            for(int j = 0;j < KUB[i].size();j++)
            {
                int reanr = KUB[i][j];
                RUB[dlar[reanr].SE].push_back(reanr);
            }
        delete [] KUB;

        LL wyn = 0;
        for(int i = n;i >= 1;i--)
            for(int j = 0;j < RUB[i].size();j++)
            {
                pair<int,int> rea = reakcje[RUB[i][j]];
                int x = min(gram[rea.FI], gram[rea.SE]);
                gram[rea.FI] -= x;
                gram[rea.SE] -= x;
                wyn += 2*x;
            }

        delete [] RUB;
        delete [] dlar;
        return wyn;
    }

    void DFS(int x)
    {
        for(int i = 0;i < KR[x].size();i++)
            dlar[KR[x][i]].FI = obecnysyn[dlar[KR[x][i]].SE];
        for(int i = 0;i < syn[x].size();i++)
        {
            obecnysyn[x] = syn[x][i];
            DFS(syn[x][i]);
        }
    }
};

namespace WczytajPrzeksztalcIWywolajOblicz // Wczytuje dane i przekształca na drzewo z wierzchołkami ponumerowanymi według czasów wejścia
{
    void DFS(int x);

    int n,m,k;
    int *gram;
    pair<int,int> *reakcje;

    int *ojc;
    vector<int> *syn;

    int obecnynr = 0;
    int *nnr;

    int *ngram;
    int *nojc;

    void main()
    {
        scanf("%d%d%d", &n, &m, &k);

        syn = new vector<int>[n+7];
        ojc = new int[n+7];
        gram = new int[n+7];
        nnr = new int[n+7];
        reakcje = new pair<int,int>[k+7];
        fill(ojc+0,ojc+n+1,0);
        //fill(nowynr+0, nowynr+n+1, 0);

        for(int i = 1;i <= n;i++)
            scanf("%d", &gram[i]);

        for(int i = 1;i <= m;i++)
        {
            int a,b;
            scanf("%d%d", &a, &b);
            syn[b].push_back(a);
            //assert(ojc[a] == 0);
            ojc[a] = b;
        }

        for(int i = 1;i <= k;i++)
        {
            int a,b;
            scanf("%d%d", &a, &b);
            reakcje[i] = MP(a,b);
        }

        nnr[0] = 0;
        for(int i = 1;i <= n;i++)
            if(ojc[i] == 0)
                DFS(i);

        /*cerr << "Nnr: ";
        for(int i = 1;i <= n;i++)
            cerr << nnr[i] << " ";
        cerr << endl;*/

        delete [] syn;

        ngram = new int[n+7];
        for(int i = 1;i <= n;i++)
            ngram[nnr[i]] = gram[i];
        delete [] gram;

        nojc = new int[n+7];
        for(int i = 1;i <= n;i++)
            nojc[nnr[i]] = nnr[ojc[i]];
        delete [] ojc;

        for(int i = 1;i <= k;i++)
        {
            reakcje[i].FI = nnr[reakcje[i].FI];
            reakcje[i].SE = nnr[reakcje[i].SE];
            if(reakcje[i].FI > reakcje[i].SE) swap(reakcje[i].FI, reakcje[i].SE);
        }

        delete [] nnr;

        LL wyn = Oblicz::main(n, k, ngram, nojc, reakcje);
        printf("%lld\n", wyn);

        delete [] ngram;
        delete [] nojc;
        delete [] reakcje;
    }

    void DFS(int x)
    {
        nnr[x] = ++obecnynr;
        for(int i = 0;i < syn[x].size();i++)
            DFS(syn[x][i]);
    }
};

int main()
{
    WczytajPrzeksztalcIWywolajOblicz::main();
    return 0;
}