/*************************************************************************

     > File Name: 4923.cpp

     > Author: Stomach_ache

     > Mail: sudaweitong@gmail.com

     > Created Time: 2014年08月08日 星期五 22时27分38秒

     > Propose:

  ************************************************************************/

 #include <cmath>

 #include <string>

 #include <cstdio>

 #include <fstream>

 #include <cstring>

 #include <iostream>

 #include <algorithm>

 using namespace std;

 const double eps = 1e-;

 const int maxn = ;

 int n;

 int a[maxn], st[maxn];

 struct node {

     double x; //区间均值

     int l, r, one; //区间范围及1的个数

 }A[maxn];

 // unite i to j

 void unite(int i, int j) {

       A[j].l = A[i].l;

     A[j].x = A[j].one + A[i].one + 0.0;

     A[j].x /= A[j].r - A[j].l + ;

     A[j].one = A[i].one + A[j].one;

 }

 double solve() {

       int len = ;

     for (int i = ; i <= n; i++) {

           A[len].x = a[i] + 0.0;

         A[len].l = i;

         i++;

         while (i <= n && a[i] == a[i-]) i++;

         A[len].r = i - ;

         i--;

         if (a[i]) A[len].one = A[len].r - A[len].l + ;

         else A[len].one = ;

         len++;

     }

     int top = ;

     for (int i = ; i < len; i++) {

           while (top && A[i].x < A[st[top-]].x) {

               unite(st[top-], i);

             top--;

         }

         st[top++] = i;

     }

     double ans = 0.0;

     for (int i = ; i < top; i++) {

           for (int j = A[st[i]].l; j <= A[st[i]].r; j++) {

               ans += (a[j] - A[st[i]].x) * (a[j] - A[st[i]].x);

         }

     }

     return ans + eps;

 }

 int main(void) {

       int t;

     scanf("%d", &t);

     while (t--) {

           scanf("%d", &n);

         for (int i = ; i <= n; i++) scanf("%d", a + i);

         printf("%.6f\n", solve());

     }

     return ;

 }