#include <fstream>
#include<deque>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
int n, k, i,v[5000001];
long long s;
deque<int> w;
int main(){
    in >> n >> k;
    for( i = 1; i <= n; i ++ ){
        in >> v[i];
    }
    for( i = 1; i <= n; i ++ ){
        while( w.empty() == 0 && v[w.back()] > v[i]){
            w.pop_back();
        }
        w.push_back(i);
        if( w.front() <= i-k ){
            w.pop_front();
        }
        if( i >= k ){
            s+=v[w.front()];
        }
    }
    out<<s;
    return 0;
    
}