杭电2187

#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
struct food{
    int price;
    int weight;
};
food a[1005];
int cmp(food a,food b)
{
    return a.price<b.price;
}
int main()
{
    int t,n,m;
    double sum;
    while(cin>>t)
    {
        while(t--)
        {
            sum=0;
            cin>>n>>m;
            for(int i=0;i<m;i++)
                cin>>a[i].price>>a[i].weight;
                sort(a,a+m,cmp);
                for(int i=0;i<m;i++){
                    if(n>0)
                {
                    if((n*1.00/a[i].price)>a[i].weight)//如果剩余的金钱够把最便宜的豆子都买了
                   {
                       sum=sum+a[i].weight;
                       n=n-a[i].price*a[i].weight;//剩余的钱
                       a[i].weight=0;
                   }
                   else
                   {
                       sum=sum+n*1.00/a[i].price;
                       n=0;
                   }
                }
                }
                printf("%.2lf\n",sum);
        }
    }
}