#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;
}