#include <fstream>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,i,p,u,v[5000001],q[5000001];
long long s;
int main()
{
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>v[i];

    p=1;
    u=0;
    for(i=1;i<=n;i++){
        while(p<=u&&v[i]<v[q[u]]){
            u--;
        }
        q[++u]=i;
        while(p<=u&&q[u]-q[p]>=k)
            p++;

        if(i>=k){
            s+=v[q[p]];
        }


    }
    fout<<s;
    return 0;
}