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#include <cstdio>
#include <algorithm>
#include <vector>
#include <cassert>

#define fru(j,n) for(int j=0;j<n;++j)
#define tr(it,x) for(typeof(x.begin()) it=x.begin();it!=x.end();++it)
#define x first
#define y second

using namespace std;

typedef long long LL;
typedef pair<int,int> pii;

const int MAXN= 500005;

int ILE[MAXN];
int D[MAXN][2];
int REP[MAXN],KTO[MAXN];
int REA[MAXN][2];

int find(int x)
{
	return REP[x]==x?x:(REP[x]=find(REP[x]));
}
vector<pii> ZAP[MAXN];
vector<int> ROB[MAXN];
LL ret;int n;

void dfs(int u)
{
//	printf("dfs(%d)\n",u);
	tr(it,ZAP[u]) if(REP[it->x]!=-1) ROB[find(it->x)].push_back(it->y);
	REP[u]=u;
	if(u>=n) fru(j,2)
	{
		int u2=D[u][j];
//		printf("z %d ide do %d\n",u,u2);
		dfs(u2);
		REP[u2]=u;
		assert(find(u)==u);
	}
	sort(ROB[u].begin(),ROB[u].end());
	tr(it,ROB[u])
	{
		int a=REA[*it][0],b=REA[*it][1],
			e=min(ILE[a],ILE[b]);
		ILE[a]-=e;
		ILE[b]-=e;
		ret+=e;
	}
}

int main()
{
	int m,k;
	scanf("%d%d%d",&n,&m,&k);
	fru(i,n) scanf("%d",&ILE[i]);
	int u=n;
	fru(i,n) KTO[i]=i;
	fru(i,m)
	{
		int a,b;
		scanf("%d%d",&a,&b);
		--a;--b;
		D[u][0]=KTO[a];
		D[u][1]=KTO[b];
		KTO[b]=u;
		u++;
	}
	fru(i,k) fru(j,2) scanf("%d",&REA[i][j]);
	fru(i,k) fru(j,2) REA[i][j]--;
	fru(i,k) fru(j,2) ZAP[REA[i][j]].push_back(pii(REA[i][j^1],i));
	fru(i,u) REP[i]=-1;
	for(int i=u-1;i>=0;--i) if(REP[i]==-1) dfs(i);
	printf("%lld\n",ret*2);
	return 0;
}