#include <bits/stdc++.h>

using namespace std;

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

int N, K;
deque < int > D;

int main(){

    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);

    scanf("%d%d", &N, &K);
    int S=0, Min;
    for(int i=1, x; i<=K; i++){
        scanf("%d", &x);
        D.push_front(x);
    }
    Min = *min_element(D.begin(), D.end());
    S += Min;

    for(int i=K+1, x; i<=N; i++){
        scanf("%d", &x);
        D.pop_back();
        D.push_front(x);
        Min = *min_element(D.begin(), D.end());
        S += Min;
    }

    printf("%d", S);

    return 0;
}