#include <fstream>
#define dim 5000010
using namespace std;
long long a[dim];
long long d[dim];
long long i,n,k,p,u,s;

int main() {
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin>>n>>k;
    for (i=1;i<=n;i++) {
        fin>>a[i];
    }
    p=1;
    for (i=1;i<=n;i++) {
        while (p<=u&&a[i]<a[d[u]]) u--;
        d[++u]=i;
        if (i-d[p]+1==k+1) p++;
        if (i>=k) s+=a[d[p]];
    }
    fout<<s;
    return 0;
}