#include <iostream>
#include <cstdint>

#define MIN(a, b) a < b ? a : b
#define MAX(a, b) a > b ? a : b

using namespace std;

// subtask 4 only
int main() {
	int n, k;
	int bins[200000] = {};
	int total = 0;

	cin >> n;
	cin >> k;

	int l = n, r = 0; // left and right ends of the interval

	int bin;
	int amount;

	for (int i = 0; i < n; i++) {
		cin >> amount;

		bins[i] = amount;
	}

	for (int i = 0; i < k; i++) {
		cin >> bin;
		cin >> amount;

		bins[bin] -= amount;

		l = MIN(l, bin);
		r = MAX(r, bin);
	}

	for (int i = l; i <= r; i++) {
		total += bins[i];
	}

	cout << total;
	
	return 0;
}