#include<bits/stdc++.h>
using namespace std;
inline int read() {
    int x = 0, f = 1; char ch = getchar();
    while(ch<'0' || ch>'9') { if(ch=='-') f=-1; ch=getchar(); }
    while(ch>='0'&&ch<='9') { x=(x<<3)+(x<<1)+(ch^48); ch=getchar(); }
    return x * f;
}
const int N = 1e5+7;
int n,a;
int b[N],f[N];
int main()
{
	n = read(), a = read();
	for(int i=1;i<=n;++i) b[i] = read();
	b[0] = b[n], b[n+1] = b[1];
	for(int i=1;i<=n;++i) f[i] = -(b[i-1] + b[i] + b[i+1]);
	sort(f+1, f+1+n);
	int ans = 0;
	for(int i=1;i<=a;++i) ans += -f[i];
	ans += 3*(n-a);
	printf("%d\n",ans);
	return 0;
}