#include <bits/stdc++.h>
using namespace std;
#define int long long
constexpr int N = 30010, M = 10010;
constexpr int inf = 1E18, mod = 100003;
int n, m, w[N], v[N], dp[N];
inline void Main() {
    cin >> m >> n;
    for (int i = 1; i <= n; i ++) {
        cin >> w[i] >> v[i];
        v[i] *= w[i];
    }
    for (int i = 1; i <= n; i ++) {
        for (int j = m; j >= w[i]; j --) {
            dp[j] = max(dp[j], dp[j - w[i]] + v[i]);
        }
    }
    cout << dp[m] << '\n';
}
signed main() {    
    cin.tie(nullptr)->sync_with_stdio(false);
    int T = 1; 
    while(T --) Main();
    return 0;
}