#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1e7 + 10;
int v[N];
int w[N];
int f[N];

signed main() {
	int m, n, d;
	cin >> m >> n >> d;
	for (int i = 1; i <= d; i++)
		cin >> v[i] >> w[i];
	int sum = m;
	for (int k = 1; k <= n; k++) {
		memset(f, 0, sizeof(f));
		for (int i = 1; i <= d; i++) {
			for (int j = v[i]; j <= sum; j++) {
				f[j] = max(f[j], f[j - v[i]] + w[i]);
			}
		}
		sum += f[sum];
	}
	cout << sum << "\n";

	return 0;
}