#include <iostream>
using namespace std;
int T, M;
struct cave {
	int t, val;
}med[101];
int dp[101][101];
int solve() {
	memset(dp, 0, sizeof(dp));
	for (int i = 0; i < M; ++i) {
		for (int j = 0; j <= T; j++) {
			if (med[i].t > j) {
				dp[i][j] = dp[i - 1][j];
			}
			else {
				dp[i][j] = max(dp[i - 1][j],
					dp[i - 1][j - med[i].t] + med[i].val);
			}
		}
	}
	return dp[M - 1][T];
}
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	cin >> T >> M;
	for (int i = 0; i < M; ++i) {
		cin >> med[i].t >> med[i].val;
	}
	cout << solve();
	return 0;
}