#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
long long int n,k,p,minim;
deque<pair<long long int,long long int>> dq;
int main(){
    fin>>n>>k;
    for(int i=0;i<n;i++){
        fin>>p;
        while(!dq.empty()&&dq.back().second>=p){
            dq.pop_back();
        }
        dq.push_back({i,p});
        while(!dq.empty()&&i-dq.front().first+1>k){
            dq.pop_front();
        }
        if(i>=k-1){
            minim+=dq.front().second;
        }
    }
    fout<<minim;
    return 0;
}