文件目录

#include <bits/stdc++.h>
using namespace std;
struct node
{
    double n, v, p;
    bool operator<(const node &b) const
    {
        return p > b.p;
    }
} a[10005];
int k, s;
double w;
int main()
{
    cin >> k;
    while (k--)
    {
        cin >> w >> s;
        for (int i = 1; i <= s; i++)
        {
            cin >> a[i].n >> a[i].v;
            a[i].p = a[i].v / a[i].n;
        }
        sort(a + 1, a + s + 1);
        double sum = 0;
        for (int i = 1; i <= s; i++)
        {
            if (w >= a[i].n)
            {
                w -= a[i].n;
                sum += a[i].v;
            }
            else
            {
                sum += a[i].p * w;
                break;
            }
        }
        printf("%.2lf\n", sum);
    }
    return 0;
}