2018 Wannafly summer camp Day3--Shopping

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
using namespace std;
int t, n, m,a[1005], b, cnt;
double ans;
bool cmp(int a, int b){return a > b;}
int main(void) {
    cin >> t;
    while (t-- > 0) {
        cin >> n >> m;
        cnt = 0, ans = 0;
        for (int i = 0; i < n; i++) {
            cin >> a[i] >> b;
            if (b == 1)
                cnt++;
        }
        sort(a, a + n, cmp);
        cnt = min(cnt, m);
        for (int i = 0; i < n; i++) {
            if (i < cnt)
                ans += a[i] * 0.5;
            else
                ans += a[i];
        }
        printf("%.1lf\n", ans);
    }
    return 0;
}