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#include <iostream>
#include <map>
#include <vector>
#include <set>
#include <algorithm>

struct Substance
{
	unsigned int id;
	unsigned long int quantity;
};

struct Reaction
{
	Reaction(unsigned int first, unsigned int second): 
	  firstSubstance(std::min(first, second)),
	  secondSubstance(std::max(first, second)) {};
	unsigned int firstSubstance;
	unsigned int secondSubstance;
};

struct Step
{
	unsigned int fromVial;
	unsigned int toVial;
};

struct CompareById
{
	bool operator()(const Substance& a, const Substance& b)
	{
		return a.id < b.id;
	}
};

struct CompareReactions
{
	bool operator()(const Reaction& a, const Reaction& b)
	{
		return (a.firstSubstance < b.firstSubstance) or
		       ((a.firstSubstance == b.firstSubstance) and (a.secondSubstance < b.secondSubstance));   
	}
};
std::map< Reaction, unsigned int, CompareReactions > priorities;
Substance substance[200001];
Step step[200001];
std::set< Substance, CompareById > vial[200001];

struct CompareReactionPriorities
{
	bool operator()(const Reaction& a, const Reaction& b)
	{
		return priorities[a] < priorities[b];   
	}
} compareRP;

unsigned long long int mixVials(unsigned int from, unsigned int to)
{
	std::vector<Reaction> actualReactions;
	std::vector<bool> inversions;
  unsigned long long int result = 0;
  std::set< Substance, CompareById >::iterator firstIt;
  std::set< Substance, CompareById >::iterator secondIt;
  
  for (firstIt=vial[from].begin(); firstIt!=vial[from].end(); ++firstIt)
  {
  	if (firstIt->quantity > 0)
  	{
    	for (secondIt=vial[to].begin(); secondIt!= vial[to].end(); ++secondIt)
    	{
    		if (secondIt->quantity > 0)
    		{
      		Reaction toReact(firstIt->id, secondIt->id);
      		if (priorities.find(toReact) != priorities.end())
  	    	{
  		    	actualReactions.push_back(toReact);
  		    	inversions.push_back(firstIt->id != toReact.firstSubstance);
    		  }
  		  }
  	  }
  	}
  }
  std::sort(actualReactions.begin(), actualReactions.end(), compareRP);
  for(unsigned int i=0; i<actualReactions.size(); ++i)
  {
  	Substance first = {actualReactions[i].firstSubstance, 0};
  	Substance second = {actualReactions[i].secondSubstance, 0};
  	if (inversions[i])
  	{
      firstIt = vial[from].find(second);
			secondIt = vial[to].find(first);    	
    }
    else
  	{
      firstIt = vial[from].find(first);
			secondIt = vial[to].find(second);    	
    }
    if ((firstIt != vial[from].end()) and (secondIt != vial[to].end()) and 
		    (firstIt->quantity >0) and (secondIt->quantity > 0))
    {
      unsigned long int newResidue = std::min(firstIt->quantity, secondIt->quantity);
      result += (2*newResidue);
      Substance firstChanged = {firstIt->id, firstIt->quantity - newResidue};
      Substance secondChanged = {secondIt->id, secondIt->quantity - newResidue};

      vial[to].erase(secondIt);
      if (secondChanged.quantity > 0)
        vial[to].insert(secondChanged);

      vial[from].erase(firstIt);
      if (firstChanged.quantity > 0)
        vial[from].insert(firstChanged);
    }
  }
  for (firstIt=vial[from].begin(); firstIt!=vial[from].end(); ++firstIt)
  {
  	if (firstIt->quantity > 0)
  	  vial[to].insert(*firstIt);
  }
  return result;					      
};

int main()
{
	unsigned int substances;
	std::cin >> substances;
	unsigned int steps;
	std::cin >> steps;
	unsigned int reactions;
	std::cin >> reactions;
	for (unsigned int i=1; i<=substances; ++i)
	{
    substance[i].id = i;
		std::cin >> substance[i].quantity;
		vial[i].insert(substance[i]); 		
	}
	for (unsigned int i=0; i<steps; ++i)
	{
		std::cin >> step[i].fromVial;
		std::cin >> step[i].toVial;
	}
	for (unsigned int i=0; i<reactions; ++i)
	{
		unsigned int first;
		std::cin >> first;
		unsigned int second;
		std::cin >> second;
		Reaction toAdd(first, second);
		priorities[toAdd] = i;
	}
	unsigned long long int residue = 0;
	for (unsigned int i=0; i<steps; ++i)
	{
		residue += mixVials(step[i].fromVial, step[i].toVial);
	}
	std::cout << residue;
	return 0;
}