RE求助！！！！！！！！！！！！！！！！

#include <bits/stdc++.h>
using namespace std;
int n,m;
struct T
{
	int p,a;
}c[100005];
bool cmp(T q,T r)
{
	return q.a / q.p > r.a / r.p;
}
int main()
{
	cin >> n >> m;
	for (int i = 1;i <= m;i++)
	{
		cin >> c[i].p >> c[i].a;
	}
	sort(c + 1,c + n + 1,cmp);
	long long sum = 0,i = 1;
	while (sum >= n)
	{
		sum += c[i].a * c[i].p;
		i++;
	}
	cout << sum;
}