third

#include <bits/stdc++.h>
using namespace std;
multiset<int> M;
multiset<int> :: iterator it;
ifstream  fin("third.in");
ofstream fout("third.out");
int n,k,a[100003];

int main()
{
    int i;
    long long suma = 0;
    fin >> n >> k;
    for (i = 1; i <= n; i++)
        fin >> a[i];
    for (i = 1; i <= k; i++)
        M.insert(a[i]);
    it = M.begin();
    it++;
    it++;
    suma += *it;
    for (i = k + 1; i <= n; i++)
    {
        M.insert(a[i]);
        it = M.find(a[i - k]);
        M.erase(it);
        it = M.begin();
        it++;
        it++;
        suma += *it;
    }
    fout << suma << "\n";
    fin.close();
    fout.close();
    return 0;
}