#include <bits/stdc++.h>

using namespace std;

int v[5000001];
deque<int> dq;

int main(){
    ifstream cin( "deque.in" );
    ofstream cout( "deque.out" );
    int n, i, ans, k;
    cin >> n >> k;
    for( i = 0; i < n; i++ )
        cin >> v[i];
    ans = 0;
    for( i = 0; i < n; i++ ){
        while( !dq.empty() && v[dq.back()] >= v[i] )
          dq.pop_back();
        dq.push_back(i);
        if( dq.front() == i - k )
          dq.pop_front();
        if( i >= k - 1 )
          ans += v[dq.front()];
    }
    cout << ans;
    return 0;
}