#include <fstream.h>
#define nmax 100
ifstream fin("deque.in");
ofstream fout("deque.out");


struct coada{int info, ind; coada *st, *dr;};

coada *c,*u,*p;
long n,k,x, d[nmax];
long s;


int main()
{fin>>n>>k;

for (long i=1;i<=n;i++)
fin>>a[i];

p=u=1;
d[1]=1;


for (i=2;i<=n;i++)
{

while (p<=u && a[d[u]]>=a[i]) //sterg din capat toate elem >= cu elem nou
u++;
d[u]=i;

if (d[p]==k-i) p++;

s+=a[d[i]];
}



fout<<s;
fout.close();
return 0;
}