#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define fi first
#define in inline
#define se second
#define mp make_pair
#define pb push_back
const int N = 1e5+10;

ll read(){
	ll x = 0,f = 1;char c = getchar();
	for(;c < '0' || c > '9';c = getchar())if(c == '-')f = -1;
	for(;c >= '0' && c <= '9';c = getchar())x = (x<<1) + (x<<3) + c-'0';
	return x * f;
}

int n,m;
int a[N];

void solve(){
	int n = read();
	for(int i = 1;i <= n;i++)a[i] = read();
	int mx = -1,se = -1,mi = 1e9+10;
	for(int i = 1;i <= n;i++){
		mi = min(mi,a[i]);
		mx = max(mx,a[i]);
	}
	for(int i = 1;i <= n;i++)
		if(a[i] < mx)se = max(se,a[i]);
	if(se == -1)return printf("0\n"),void();
	printf("%d\n",max(mx - mi,se));
}
int main(){
	freopen("mod.in","r",stdin);
	freopen("mod.out","w",stdout);
	int t = read();
	while(t--)solve();

	return 0;

}