AC

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {

int n, m;
cin >> n >> m;
vector<int> dp(n + 1, 0);

for (int i = 0; i < m; ++i) {
    int v, p;
    cin >> v >> p;
    int value = v * p;
    for (int j = n; j >= v; --j) {
        dp[j] = max(dp[j], dp[j - v] + value);
    }
}

cout << dp[n] << endl;
return 0;

}