#include <iostream>
#include <fstream>
#include <set>
using namespace std;

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

multiset <int> v;
int a[5000005];

int main()
{
    int n, k; fin >> n >> k;
    for(int i = 1; i <= k; ++i) {
        fin >> a[i];
        v.insert(a[i]);
    }
    long long ans = *v.begin();
    for(int i = k+1; i <= n; ++i) {
        fin >> a[i];
        v.erase(v.find(a[i-k]));
        v.insert(a[i]);
        ans += 1ll * *v.begin();
    }
    fout << ans;
    return 0;
}