#include <fstream>
#include <queue>
 
using namespace std;
 
ifstream fin("deque.in");
ofstream fout("deque.out");
 
deque<int> Q;
int n, k;
long long int v[5000005], suma;
 
int main() {
    fin >> n >> k;
    for(int i = 1; i <= n; i++) {
    	fin >> v[i];
    	while(!Q.empty() && v[i] <= v[Q.back()]) {
        	Q.pop_back();
        }
        Q.push_back(i);
        if(Q.front() <= i - k) {
            Q.pop_front();
        }
        if(i >= k) {
            suma += v[Q.front()];
        }
    }
    fout << suma;
	return 0;
}