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

int main(){
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    unsigned int n, k, i, j;
    long long val, sum = 0, min = INT64_MAX;
    deque<long long> deq;
    fin>>n>>k;

    for(i = 0; i < n; i++){
        fin>>val;
        
        if(deq.size() == k){
            for(j = 0; j < k; j++)
                if(deq[j] < min)
                    min = deq[j];
            sum += min;
            min = INT64_MAX;
            deq.pop_front();
        }
        
        deq.push_back(val);
    }

    if(deq.size() == k){
        for(j = 0; j < k; j++)
            if(deq[j] < min)
                min = deq[j];
        sum += min;
        min = INT64_MAX;
        deq.pop_front();
    }

    fout<<sum;


    return 0;
}