#include <stdio.h>
int main()
{
int zu = 0;
int cnt[20] = {};
float temp[20][50] = {};
scanf("%d", &zu);
for (int i = 0; i < zu; ++i){
scanf("%d", &cnt[i]);
for (int k = 0; k < cnt[i]; ++k){
scanf("%f", &temp[i][k]);
}
}
for (int i = 0; i < zu; ++i){
int n = cnt[i];
if (n & 1){
printf("%.2f\n", temp[i][n / 2]);
}
else{
n /= 2;
printf("%.2f\n", (temp[i][n] + temp[i][n - 1]) / 2.f);
}
}
return 0;
}