#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define Rep(b, e, i) for(int i = b; i <= e; i++) #define Repr(e, b, i) for(int i = e; i >= b; i--) #define rep(n, i) Rep(0, n-1, i) #define repr(n, i) Repr(n-1, 0, i) #define all(v) (v).begin(), (v).end() #define pb(v) push_back(v) #define uniq(v) (v).erase(unique(all(v)),(v).end()) #define bitcnt(x) __builtin_popcount(x) #define fst first #define snd second #define Pqaz(T) priority_queue,greater> #define Pqza(T) priority_queue #define put(x) cout << x; #define putsp(x) cout << x << ' '; #define putln(x) cout << x << endl; #define ENJYU std::ios::sync_with_stdio(false);std::cin.tie(0); typedef long long ll; typedef pair llP; typedef pair intP; typedef complex comp; typedef vector vec; typedef vector vecll; typedef vector vecd; typedef vector mat; typedef vector matll; typedef vector matd; //vector の中身を出力 template ostream &operator<<(ostream &o,const vector&v) {o<<"{";for(int i=0;i<(int)v.size();i++)o<<(i>0?", ":"")<> N >> M; vecll as(N-1); ll A; cin >> A; rep(N-1, i) cin >> as[i]; if (N == 2) { cout << as[0] << endl; return; } sort(all(as)); if (as[N-2] + A < as[N-3] + as[N-4] && M == 1) { cout << -1 << endl; return; } int ng = -1, ok = N-2; while (abs(ng-ok) > 1) { int mid = (ok+ng) / 2; ll score = as[mid] + A; vecll copy = as; copy[mid] = INFL; sort(all(copy)); int cnt = 0; repr(N-1, i) { if (copy[i] + copy[i-1] > score) { cnt++; i--; } else { break; } } (cnt <= M-1 ? ok : ng) = mid; //cout << cnt << ' ' << mid << endl; } cout << as[ok] << endl; } int main(void){ solve(); //cout << "yui(*-v・)yui" << endl; return 0; }