#include <fstream>
#include <queue>
#include <set>

using namespace std;

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

typedef long long llong;

queue<llong> q;
multiset<llong> my_set;

llong N, K, sum, val;

int main()
{
    in >> N >> K;
    for(llong i = 1; i <= K; ++i)
    {
        in >> val;
        my_set.insert(val);
        q.push(val);
    }
    for(llong i = 1; i <= N - K; ++i)
    {
        sum += *my_set.begin();
        my_set.erase(my_set.find(q.front()));
        in >> val;
        my_set.insert(val);
        q.pop();
        q.push(val);
    }
    out << sum + *my_set.begin();
    return 0;
}