#include <iostream>
using namespace std;
const int k=1e7+5;
int dp[k];
int a[10100], b[10100];
int main() {
	int T, M;
	cin >> T >> M;
	for (int i = 1; i <= M; i++) cin >> a[i] >> b[i];
	for (int i = 1; i <= M; i++) {
		for (int j = a[i]; j <= T; j++) {
			dp[j] = max(dp[j], dp[j - a[i]] + b[i]);
		}
	}
	cout << dp[T];
	return 0;
}

90分记录