#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;
using pint = pair<lint, lint>;
using vp = vector<pint>;

int main() {
	lint N, K, no;
	cin >> N >> K >> no;
	vi v(N-1);
	vin(v);

	lint a=0, b=N-1, c=N-1, x, y, z;
	vp p(N-1);
	rep(i, N-1) p[i] = {v[i], -i};
	sort(all(p), greater());
	rep(i, K-1) {
		tie(x, y) = p[i];
		y = -y;
		a += x;
		if (y%2 == 0) chmin(b, y);
		else chmin(c, y);
	}
	// list(a)
	// list(b)
	// list(c)
	x = 0;
	rep(i, min(b, c)) {
		if (i%2 == 0) chmax(x, v[i]);
	}
	if (x == 0) a += p[K-1].first;
	else a += x;
	std::cout << a << '\n';
}