#include <iostream>
#include <fstream>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

const int dim=5000001;

int main()
{
    int n, x, i, v[dim], deq[dim], rez[dim], l=1, r=0;
    long long s=0;
    f>> n >> x;
    for(i=1; i<=n; i++){
        f>> v[i];
    }
    for(i=n; i>=1; i--){
        if(deq[l]==i+x){
            l++;
        }
        while(r>=l && v[deq[r]]>=v[i]){
            r--;
        }
        deq[++r]=i; rez[i]=v[deq[l]];
    }
    for(i=1; i<=n-x+1; i++){
        s+=rez[i];
    }
    g<< s;

    return 0;
}