#include <iostream>
#include <fstream>
#include <cstring>
#include <climits>
#include <deque>
#define dmax 5000001

using namespace std;

ifstream fin ("deque.in");
ofstream fout ("deque.out");

deque<int> d;
long long v[dmax];

int main()
{
    long long n, k, s = 0, i;
    char c;
    fin>>n>>k;
    for(i = 1; i <= n; ++i)
        fin>>v[i];
    for(i = 1; i <= n; ++i){
        while (!d.empty() and v[i ]<= v[ d.back() ])
            d.pop_back();
        d.push_back(i);
        if( d.front() <= i-k) d.pop_front();
        if( i >= k) s += v[d.front()];
    }
    fout<<s;
    return 0;
}