// https://goo.gl/fBmFxu
#include <bits/stdc++.h>
using namespace std;

#define NMAX        5000005
#define MMAX        200009
#define kInf        (1 << 30)
#define kInfLL      (1LL << 60)
#define kMod        666013
#define edge pair<int, int>
#define x first
#define y second

#define USE_FILES "MLC"

#ifdef USE_FILES
#define cin fin
#define cout fout
ifstream fin("input");
ofstream fout("output");
#endif

// number of tests from "in"
int test_cnt = 1;
void clean_test();

// your global variables are here
int N, K, a[NMAX];
long long sol;
deque <int> d;


// your solution is here
void solve() {
    cin >> N >> K;
    
    for (int i = 1; i <= N; ++i) {
        cin >> a[i];
        
        while (d.size() && a[d.back()] >= a[i]) {
            d.pop_back();
        }
        d.push_back(i);
        
        if (i - d.front() >= K) {
            d.pop_front();
        }

        if (i >= K) {
            sol += 1LL * a[d.front()];
        }
    }
    
    cout << sol << '\n';


    if (test_cnt > 0) {
        clean_test();
    }
}


void clean_test() {
    // clean if needed
}

int main() {
//     cin >> test_cnt;
    while (test_cnt--) {
        solve();
    }

    return 0;
}