#include<fstream>
#include<algorithm>
using namespace std;
int m,n,a,b,i,j,st,dr,x,tip;
int arb[20000000],mini;
long long sum;

void act(int r,int st,int dr,int x,int poz)
{
    if(st==dr)
    {
        arb[r]=x;
        return;
    }
   int mij=(st+dr)/2;
     if(poz<=mij) act(r*2,st,mij,x,poz);
    else act(r*2+1,mij+1,dr,x,poz);
    arb[r]=min(arb[r*2],arb[r*2+1]);
}

void inter(int r,int st,int dr,int a,int b)
{
     if (a<=st && dr<=b)
     {
          if(mini>arb[r]) mini=arb[r];
          return;
     }
    int mij=(st+dr)/2;
     if (a<=mij) inter(2*r,st,mij,a,b);
     if (mij<b) inter(2*r+1,mij+1,dr,a,b);
}

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&x);
        act(1,1,n,x,i);
    }
    a=1;
    while(m<=n)
        {
        mini=12000000;
        inter(1,1,n,a,m);
        a++,m++;
        sum+=mini;
    }
    printf("%lld",sum);
}