#include <deque>
#include <fstream>

using namespace std;

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

typedef long long i64;

const int nmax= 5000000;

deque <int> d;
int v[nmax+1];

int main(  ) {
    int n, k;
    i64 sol= 0;
    fin>>n>>k;
    for ( int i= 1; i<=n; ++i ) {
        fin>>v[i];
        while ( !d.empty() && d.front()<=i-k ) {
            d.pop_front();
        }
        while ( !d.empty() && v[d.back()]>v[i] ) {
            d.pop_back();
        }

        d.push_back(i);

        if ( k<=i ) {
            sol= sol+v[d.front()];
        }
    }
    fout<<sol<<"\n";

    return 0;
}