import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.stream.Collectors;

public class Pickpockets {

	static int maxProfit = 0;

	public static void main(String args[]) {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		String[] line1;
		String[] line2;

		List<Map.Entry<Integer, Integer>> teams = new ArrayList<>();

		try {
			line1 = br.readLine().split(" ");
			line2 = br.readLine().split(" ");

			List<Integer> days = Arrays.asList(line2).stream().map(Integer::parseInt).collect(Collectors.toList());

			int H = Integer.parseInt(line1[0]);
			int T = Integer.parseInt(line1[1]);

			for (int i = 0; i < T; i++) {
				String[] lineX = br.readLine().split(" ");

				teams.add(
						new AbstractMap.SimpleImmutableEntry<>(Integer.parseInt(lineX[0]), Integer.parseInt(lineX[1])));

			}

			maxPick(days, H, teams, 0);

			System.out.println(maxProfit);

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	static void maxPick(List<Integer> days, int H, List<Map.Entry<Integer, Integer>> teams, int profit) {

		if (days.stream().filter(d -> d > 0).findAny().isEmpty()) {
			maxProfit = max(maxProfit, profit);
			return;
		}

		for (Map.Entry<Integer, Integer> team : teams) {
			for (int i = 0; i <= H - team.getKey(); i++) {
				boolean matchE = true;
				List<Integer> newDays = new ArrayList<>(days);
				for (int j = 0; j < team.getKey(); j++) {
					if (newDays.get(j + i) > 0) {
						newDays.set(j + i, newDays.get(j + i) - 1);
						matchE = true;
					} else {
						matchE = false;
						break;
					}
				}
				if (matchE) {
					List<Entry<Integer, Integer>> newTeams = new ArrayList<>(teams);
					newTeams.remove(team);
					maxPick(newDays, H, newTeams, profit + team.getValue());
				}
			}
		}

//		maxProfit = max(maxProfit, profit);
		
		boolean same_nuly = true;
	    for (int i=0; i < H; i++){
	        if (days.get(i) > 0)
	            same_nuly = false;
	    }
	    if (same_nuly){
	        maxProfit = max(maxProfit, profit);
	    }
		
	}

	static int max(int a, int b) {
		return (a > b) ? a : b;
	}
}