#include <bits/stdc++.h>
using namespace std;

const int N = 1010;
int f[N];
int w[N], v[N];
int n, m;

int main()
{
	cin >> n >> m;
	for(int i = 1; i <= m; i++) cin >> v[i] >> w[i];
	for(int i = 1; i <= m; i++)
		for(int j = n; j >= v[i]; j--)
			f[j] = max(f[j], f[j - v[i]] + w[i]);

	cout << f[n] << endl;
	return 0;
}