#include <iostream>
#include <fstream>
#include <climits>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int v[5000001],dq[5000001],n,k,i;///deq pozitiile din v
long long s=0;
int main()
{
    fin>>n>>k;
    int st=0,dr=0;
    v[0]=INT_MIN;
    for(int i=1;i<=n;i++){
        fin>>v[i];
        while(i-dq[st]+1>k){ ///elimin de la inceput deoarece lung secv ce se termina in i este mai mare decat k
            st++;
        }
        while(st<=dr && v[i]<=v[dq[dr]]){
            dr--;
        }
        dq[++dr]=i;
        if(i>=k){
            s+=v[dq[st]];
        }
    }
    fout<<s;
    return 0;
}