1 #include<iostream>
 2 #include<algorithm>
 3 #include<vector>
 4 #include<stack>
 5 #include<queue>
 6 #include<map>
 7 #include<set>
 8 #include<cstdio>
 9 #include<cstring>
10 #include<cmath>
11 #include<ctime>
12 #define fuck(x) cout<<#x<<" = "<<x<<endl;
13 #define ls (t<<1)
14 #define rs ((t<<1)+1)
15 using namespace std;
16 typedef long long ll;
17 typedef unsigned long long ull;
18 const int maxn = 200086;
19 const int inf = 2.1e9;
20 const ll Inf = 999999999999999999;
21 const int mod = 1000000007;
22 const double eps = 1e-6;
23 const double pi = acos(-1);
24 ll num1[maxn],val1[maxn],num2[maxn],val2[maxn];
25 int n,k;
26 struct node{
27     ll num;
28     int id;
29 }a[maxn];
30 int lowbit(int x){
31     return x&(-x);
32 }
33 void update(ll *bit,int p,ll num){
34     while(p<=n){
35         bit[p]+=num;
36         p+=lowbit(p);
37     }
38 }
39
40 ll query(ll *bit,int p){
41     ll ans=0;
42     while(p>0){
43         ans+=bit[p];
44         p-=lowbit(p);
45     }
46     return ans;
47 }
48
49 bool cmp(node a,node b){
50     return a.num<b.num;
51 }
52
53 int main()
54 {
55     scanf("%d%d",&n,&k);
56     for(int i=1;i<=n;i++){
57         scanf("%lld",&a[i].num);
58         a[i].id=i;
59     }
60     sort(a+1,a+1+n,cmp);
61     ll ans=0;
62     for(int i=1;i<=n;i++){
63         int l,r;
64         if(a[i].id>=k)l=a[i].id-k+1;
65         else{l=k-a[i].id+1;}
66         if(a[i].id+k-1<=n){r=a[i].id+k-1;}
67         else{r=2*n-a[i].id-k+1; }
68         if((a[i].id+k-1 )&1){
69             ans-=query(val1,r)-query(val1,l-1);
70             ans+=a[i].num*(query(num1,r)-query(num1,l-1));
71         }
72         else{
73             ans-=query(val2,r)-query(val2,l-1);
74             ans+=a[i].num*(query(num2,r)-query(num2,l-1));
75         }
76         if(a[i].id&1){
77             update(val1,a[i].id,a[i].num);
78             update(num1,a[i].id,1);
79         }
80         else{
81             update(val2,a[i].id,a[i].num);
82             update(num2,a[i].id,1);
83         }
84     }
85     printf("%lld\n",ans);
86
87     return 0;
88 }