#include <bits/stdc++.h>   using namespace std;   int main() {     long long t;     cin >> t;     while (t--) {       long long n;       cin >> n;       vector<long long> v(n), vec;       for (int i = 0; i < n; i++) cin >> v[i];       for (int i = 0; i < n; i++) {         if (v[i] == -1) continue;         if (i - 1 >= 0 && v[i - 1] == -1) vec.push_back(v[i]);         if (i + 1 < n && v[i + 1] == -1) vec.push_back(v[i]);       }       sort(vec.begin(), vec.end());       long long num, res = -1;       if (vec.size() == 0) num = 1;       if (vec.size() == 1) num = vec[0];       if (vec.size() >= 2) num = (vec[vec.size() - 1] + vec[0]) / 2;       for (int i = 0; i < n; i++) {         if (v[i] == -1) v[i] = num;       }       for (int i = 0; i < n - 1; i++) {         res = max(res, abs(v[i] - v[i + 1]));       }       cout << res <<     << num << endl;     }     return 0;   }   