#include <stdio.h>
#include <stdlib.h>
int compare(const void *a,const void *b);
int t,n;
int suma_promieni, prev, next;
const double pi = 3.1415926535897932384626433;

int main(){

scanf("%d", &t);
getchar();

for (;t>0;t--){
scanf("%d", &n);
getchar();

int *tablica;
tablica = new int[n];

for (int i=0; i<n; i++){ 
	scanf("%d", &tablica[i]);
	getchar();
}

qsort(tablica, n, sizeof(int),compare);

for (int i=1; i<n-1; i++){

	prev = tablica[i] - tablica[i-1];
	next = tablica[i+1]-tablica[i];
	if (!suma_promieni){ suma_promieni += prev;
	i++;
	}
	else{
	if (prev > next){
		suma_promieni += next;
	}
	else {
		suma_promieni += prev;
		}
}
}
suma_promieni=0;
printf("%0.2f\n",2*pi*suma_promieni);
delete tablica; 
}
return 0;
}
int compare(const void *a,const void *b){
return ( *(int*)a - *(int*)b );
}