#include<bits/stdc++.h>
using namespace std;
int main() {
	int M, N;
	cin >> M >> N;
	int W[N + 1], C[N + 1];
	for (int i = 0; i < N; i++) {
		cin >> W[i] >> C[i];
	}
	int dp[N + 1][M + 1];
	for (int i = 0; i <= N; i++) {
		for (int j = 0; j <= M; j++) {
			if (i == 0 || j == 0) {
				dp[i][j] = 0;
			} else if (W[i - 1] <= j) {
				dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - W[i - 1]] + C[i - 1]);
			} else {
				dp[i][j] = dp[i - 1][j];
			}
		}
	}
	cout << dp[N][M] << endl;
	return 0;
}