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#include <cstdio>
#include <vector>
#include <cmath>
#include <algorithm>
#define MAXN 200005
#define MAXK 500005
#define LOGN (ceil(log(n)))
using namespace std;

int n,m,k;
int p[MAXN][50],M[MAXN];

struct col {
	int a,b,val;
	col(int a,int b,int val) : a(a), b(b), val(val){}
	bool operator < (const col &c) const {
		return val < c.val;
	}
};

struct tree {
	tree *parent;
	vector<tree*> next;
	vector<col> C;
	int f, id, pre, size;
} T[MAXN];

void p_array(int root) {
	for(int i=1;i<=n;i++) if(T[i].parent != NULL) p[i][0] = T[i].parent->id;
	p[root][0] = root;
	for(int i=1;i<=LOGN;i++) for(int k=1;k<=n;k++) p[k][i] = p[p[k][i-1]][i-1];
}

int pre_array(tree *root, int &pos) {
	root->pre = ++pos;
    root->size = 1;
	for(int i=0;i<root->next.size();i++) {
		if(root->next[i] == root->parent) continue;
		root->next[i]->parent = root;
		root->size += pre_array(root->next[i], pos);
	}
	return root->size;
}

bool descendant(tree *u, tree *v) {
	if(u->pre > v->pre && u->pre <= v->pre + v->size-1) return true;
	else return false;
}

tree* lca(tree *u, tree *v) {
	if(u == v) return u;
	if(descendant(u,v)) return v;
	if(descendant(v,u)) return u;

	int i=u->id, j=LOGN;
	while(j>=0) {
		if(descendant(v, &T[p[i][j]])) j=j-1;
		else i = p[i][j];
	}
	return &T[p[i][0]];
}

bool test(int a, tree* root) {
	if(T[a].id == root->id) return true;
	return descendant(&T[a],root);
}

long long int sim(tree* root) {
	long long int res = 0;
	sort(root->C.begin(), root->C.end());
	int j=0,i=0;
	while( j<root->next.size() && i<root->C.size() ) {
		if(root->C[i].val < root->next[j]->pre) {
			int tmp1 = root->C[i].a;
			int tmp2 = root->C[i].b;
			int d = min(T[tmp1].f, T[tmp2].f);
			T[tmp1].f -= d;
			T[tmp2].f -= d;
			res += 2*d;
			i++;
		} else {
			res += sim(root->next[j]);
			j++;
		}
	}
	for(;j<root->next.size();j++) res += sim(root->next[j]);
	for(;i<root->C.size();i++) {
		int tmp1 = root->C[i].a;
		int tmp2 = root->C[i].b;
		int d = min(T[tmp1].f, T[tmp2].f);
		T[tmp1].f -= d;
		T[tmp2].f -= d;
		res += 2*d;
	}
	return res;
}


int main() 
{
	scanf("%d %d %d",&n,&m,&k);
	
	for(int i=1;i<=n;i++) {
		scanf("%d",&T[i].f);
		T[i].id = i;
		T[i].parent = NULL;
	}
	
	int x,y;
	for(int i=0;i<m;i++) {
		scanf("%d %d",&x,&y);
		T[x].parent = &T[y];
		T[y].next.push_back(&T[x]);
	}
	tree *root = &T[y];
	p_array(root->id);
	int pos = 1;
	pre_array(root, pos);
	
	int a,b;
	for(int i=0;i<k;i++) {
		scanf("%d %d",&a, &b);
		if(test(a,root) && test(b,root)) {
			tree *tmp = lca(&T[a], &T[b]);
			int val = max(T[a].pre, T[b].pre);
			tmp->C.push_back(col(a,b,val));
		}
	}

	printf("%lld\n",sim(root));
	return 0;
}