#include <iostream> #define LENGTH 110000 #define ll long long #define MAX(a, b) ((a) > (b) ? (a) : (b)) #define MIN(a, b) ((a) < (b) ? (a) : (b)) using namespace std; int main() { int T; cin >> T; while (T--) { int n; cin >> n; int max = 0; ll sum = 0; for (int i = 0; i < n; i++) { int temp; cin >> temp; if (temp > max) { max = temp; } sum += temp; } if (n == 1) { cout << -1 << endl; } else if(max == 1) { cout << 0 << endl; } else { cout << MIN(sum - n, max) << endl; } } return 0; }