#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <limits.h>
#include <algorithm>
#include <math.h>

using namespace std;

int main()
{
	iostream::sync_with_stdio(0);
	cin.tie(0);

	long long n, k, i, t, q, j;
	cin >> n >> k;

	vector<long long> cap(n), current(n);
	for (i = 0; i < n; i++)
	{
		cin >> cap[i];
	}

	vector<vector<long long>> trash(n);
	for (i = 0; i < k; i++)
	{
		cin >> t >> q;

		trash[t].push_back(q);
	}

	long long ans = 0;

	for (i = 0; i < n; i++)
	{
		for (j = 0; j < trash[i].size(); j++)
		{
			if (j == trash[i].size() - 1)
			{
				ans += cap[i] - current[i] - trash[i][j];
			}
			else
			{
				if (cap[i] < current[i] + trash[i][j] + trash[i][j+1])
				{
					ans += cap[i] - current[i] - trash[i][j];
					current[i] = 0;
				}
				else
				{
					current[i] += trash[i][j];
				}
			}
		}
	}

	cout << ans << '\n';
}