mixing milk 더블릿

#include <stdio.h>
#include <algorithm>
#include <vector>
#include <utility>
 
using namespace std;
vector<pair<int, int> > company(6000);
 
bool compare(const pair<int, int>& a, const pair<int, int>& b) {
    if (a.first == b.first)
        return a.second < b.second;
    return a.first < b.first;
}
 
int main() {
    int n, m;
    scanf("%d %d", &m, &n);
 
    for (int i = 1; i <= n; i++) {
        int a, b;
        scanf("%d %d", &a, &b);
        company[i] = make_pair(a, b);
    }
    sort(&company[1], &company[n + 1], compare);
 
    int total = 0;
    for (int i = 1; i <= n; i++) {
        if (m >= company[i].second) {
            m -= company[i].second;
            total += (company[i].first * company[i].second);
        }
        else if (m > 0 && m < company[i].second) {
            total += (company[i].first * m);
            break;
        }
    }
    printf("%d", total);
}