//占行

include

using namespace std; int dp[105][1005];

int main() {

int T, N;
cin >> T >> N;
int t[N], v[N];
for (int i = 1; i <= N; i++)
	cin >> t[i] >> v[i];
for (int i = 1; i <= N; i++) {
	for (int j = 1; j <= T; j++) {
		if (t[i] > j)
			dp[i][j] = dp[i - 1][j];
		else
			dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - t[i]] + v[i]);
	}
}
cout << dp[N][T];
return 0;

}