#include <bits/stdc++.h>

using namespace std;

using db = double;
using s64 = long long;
using ld = long double;
using u32 = unsigned int;
using u64 = unsigned long long;

using vi = vector<int>;
using vii = vector<vi>;
using vll = vector<s64>;

using pii = pair<int, int>;
#define fi first
#define se second
#define mp(a, b) make_pair(a, b)

#define For(i, a, b) for (decay<decltype(b)>::type i = (a), _##i = (b); i <= _##i; ++i)
#define Ford(i, a, b) for (decay<decltype(a)>::type i = (a), _##i = (b); i >= _##i; --i)
#define FOR(i, a, b) for (decay<decltype(b)>::type i = (a), _##i = (b); i < _##i; ++i)
#define FORD(i, a, b) for (decay<decltype(a)>::type i = (a) - 1, _##i = (b); i >= _##i; --i)

#ifdef LOCAL
#define Debug(x...) do { cerr << "\033[32;1m" << #x << " -> "; Err(x); } while (0)
void Err() { cerr << "\033[39;0m" << endl; }
template<template<typename...> class T, typename t, typename... A>
void Err(T<t> a, A... x) { for (auto v: a) cerr << v << ' '; Err(x...); }
template<typename T, typename... A>
void Err(T a, A... x) { cerr << a << ' '; Err(x...); }
#else
#define Debug(...)
#endif

#define all(x) x.begin(), x.end()

const double PI = acos(-1);
const double eps = 1e-7;

namespace Modulo {
	// const int P = 998244353;
	const int P = 1e9 + 7;
	int Add(int x, int y) {return (x += y) >= P ? x - P : x;}
	int Dec(int x, int y) {return (x -= y) < 0 ? x + P : x;}
	int Mult(int x, int y) {return (s64) x * y % P;}
	void mult(int &x, int y) {x = (s64) x * y % P;}
	void add(int &x, int y) {if ((x += y) >= P) x -= P;}
	void dec(int &x, int y) {if ((x -= y) < 0) x += P;}
	int qpw(int x, int k = P - 2) {
		int res = 1;
		for (; k; k >>= 1, mult(x, x))
			if (k & 1) mult(res, x);
		return res;
	}
}

namespace Solver {
    const char endl = '\n';
	void main() {
		int n, k; cin >> n >> k;
		vector<int> b(n), a(n);
		for (int& v: b) cin >> v;
		int tot = 0;
		for (int i = 0; i < n; ++i) {
			int sp = b[i] + b[(i + 1) % n] + b[(i + n - 1) % n];
			int usp = 3;
			a[i] = sp - usp;
			tot += usp;
			// cerr << a[i] << " \n"[i + 1 == n];
		}
		sort(all(a), greater<int>());
		for (int i = 0; i < k; ++i) tot += a[i];
		cout << tot << endl;
	}
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	int T = 1;
	//cin >> T;
	For(_t, 1, T) {
		// cout << "Case #" << _t << ": ";
		// cout << endl;
		Solver::main();
	}
	return 0;
}