#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;
}