#include <iostream>#include <algorithm>#include <cmath>using namespace std;int n;int t;int len[111];int b[111][111];int p[111][111];int a[222222];int m;double calc(int x){    double sum(0);    for (int i=1; i<=n; i++)    {        int xiao = 2147483647;        for (int j=1; j<=len[i]; j++)            if (b[i][j] >= x) xiao = min(xiao, p[i][j]);        sum += xiao;    }    return x / sum;}int main(void){    int i,j,k,ci,cici,cicici;    for (scanf("%d", &t); t; t--)    {        scanf("%d", &n);        for (i=1; i<=n; i++)        {            scanf("%d", &len[i]);            for (j=1; j<=len[i]; j++)            {                scanf("%d%d", &b[i][j], &p[i][j]);                a[++m] = b[i][j];            }                    }        sort(a+1, a+1+m);        int left = 1, right = m, mid1, mid2;        double f1, f2;        while(left + 1 < right)        {            mid1 = (left + right) / 2;            mid2 = (mid1 + right) / 2;            f1 = calc(a[mid1]);            f2 = calc(a[mid2]);            if (f1 < f2) left = mid1;            else right = mid2;        }        printf("%.3lf\n", max(calc(a[left]), calc(a[right])));    }    return 0;}