#include<iostream> #include<cstdio> #include<algorithm> #include<cmath> #include<cstring> #include<set> #define ll long long using namespace std; const int maxn = 200010; const int inf = 0x3f3f3f3f; int main() { int t; cin >> t; while (t--) { int n, q; cin >> n >> q; int a[110]; for (int i = 0; i < n; i++) { cin >> a[i]; } sort(a, a + n); int contrast = a[n - 1] - a[0]; if (contrast > 2 * q) { printf("-1 "); } else { printf("%d ", a[0] + q); } } }
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