// Template v2
#define pb push_back
#define mp make_pair
#define first x
#define second y
#define l(x) x<<1
#define r(x) x<<1 | 1
#define P 73
#define MOD1 3000017
#define MOD2 3000541
#include<bits/stdc++.h>

using namespace std;

typedef long long LL;
typedef long double LD;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef pair<double, double> PKK;
// primes less than 100
const int PRIM[] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97};
const int CMAX = 10005;
const int MOD = 1000000007;
const int NMAX = 5000005;
const short INF16 = 32000;
const int INF = int(1e9);
const LL INF64 = LL(1e18);
const LD EPS = 1e-9, PI = acos(-1.0);

int A[NMAX], deq[NMAX], l, r, n, k;
LL rs;

void read()
{
    cin>>n>>k;
    cout<<"";
    for(int i=1; i<=n; ++i)
        cin>>A[i];
    
    l=1; r=0;
    for(int i=1; i<=n; ++i)
    {
        while(l<=r && A[i]<=A[deq[r]])
            r--;
        deq[++r]=i;
        
        if(deq[l] == i-k)
            l++;
            
        if(i>=k)
            rs+=A[deq[l]];
    }
    cout<<rs;
}

int main() {
    cin.tie(0);
    ios_base::sync_with_stdio(0);
    cout << setprecision(16) << fixed;
    
    assert(freopen("deque.in", "rt", stdin));
    assert(freopen("deque.out", "wt", stdout));
    
    read();

    return 0;
}