#include <fstream>
#include <deque>
using namespace std;

int main() {
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    int n, k, i, j, x, min = 10000001;
    long long s;
    deque<int> dq;
    fin >> n >> k;
    for(i = 1; i <= k; ++i) {
        fin >> x;
        dq.push_back(x);
        if(x < min)
            min = x;
    }
    s = min;
    for(; i <= n; ++i) {
        fin >> x;
        dq.push_back(x);
        dq.pop_front();
        min = 10000001;
        for(j = 0; j < k; ++j)
            if(dq[j] < min)
                min = dq[j];
        s += min;
    }
    fout << s;
}