#include <iostream>
using namespace std;
const int N = 1010;
int f[N];
int v[N], w[N];
int n, m;
int main()
{
scanf("%d%d", &m, &n);
for (int i = 1; i <= n; i ++ ) scanf("%d%d", &v[i], &w[i]);
for (int i = 1; i <= n; i ++ )
for (int j = m; j >= v[i]; j -- )
f[j] = max(f[j], f[j - v[i]] + w[i]);
printf("%d\n", f[m]);
return 0;
}