c

#include <iostream>
#include<bits/stdc++.h>
#include<utility>
#define ll long long
#define ull unsigned long long
#define pi  3.14159

#define OO  2000000000
//#define ceil(w, m) (((w) / (m)) + ((w) % (m) ? 1 : 0))
using namespace std;

void yasmeen_fakhri(){
  ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
  #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
  #endif
}


void solve(){

        ll ch=INT_MIN;
        ll n; cin>>n;
        ll arr[n];
        for(int i=0;i<n;i++){
            cin>>arr[i];
        }
        for(int i=0;i<(n-1);i++){
            if((arr[i]*arr[i+1])+(arr[i]-arr[i+1])>ch) {
                ch=(arr[i]*arr[i+1])+abs((arr[i]-arr[i+1]));
               }
        }
                cout<<ch<<"\n";

}

int main() {
   yasmeen_fakhri();

int test =1;
cin>>test;
while(test--){
 solve();

}
return 0;
}