#include <iostream>
#include <algorithm>
using namespace std;

long long N, K;
long long A[1 << 18], B[1 << 18];
long long par[1 << 18][22];

bool solve(long long border) {
	for (int i = 0; i <= 2 * N; i++) {
		int pos1 = lower_bound(B, B + 2 * N, B[i] + border) - B;
		par[i][0] = pos1;
	}
	for (int i = 0; i <= 20; i++) {
		for (int j = 0; j <= 2 * N; j++) par[j][i + 1] = par[par[j][i]][i];
	}

	for (int i = 0; i < N; i++) {
		int cx = i;
		for (int j = 20; j >= 0; j--) {
			if ((K / (1LL << j)) % 2 == 1) cx = par[cx][j];
		}
		if (cx <= i + N) return true;
	}
	return false;
}

int main() {
	cin >> N >> K;
	for (int i = 0; i < N; i++) cin >> A[i];
	for (int i = N; i <= 2 * N; i++) A[i] = A[i - N];
	for (int i = 0; i <= 2 * N; i++) B[i + 1] = B[i] + A[i];

	long long cl = 0, cr = (1LL << 50), cm, maxn = 0;
	for (int i = 0; i < 53; i++) {
		cm = (cl + cr) / 2LL;
		bool I = solve(cm);
		if (I == true) { maxn = max(maxn, cm); cl = cm; }
		else { cr = cm; }
	}
	cout << maxn << endl;
	return 0;
}