#include <bits/stdc++.h> //JuniorMonster a.k.a Sho10
#define ll long long int
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define all(a) (a).begin(), (a).end()
#define sz size
#define f first
#define s second
#define pb push_back
#define er erase
#define in insert
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod 1000000007
#define PI 3.14159265359
#define CODE_START  ios_base::sync_with_stdio();cin.tie();cout.tie();
using namespace std;
ll n,k,a[5000005],ans=0,v[5000005];
int32_t main(){
CODE_START;
ifstream cin("deque.in");
ofstream cout("deque.out");
cin>>n;
cin>>k;
for(ll i=1;i<=n;i++)
{
    cin>>a[i];
}
ll s1=1,s2=0;
for(ll i=1;i<=n;i++){
        while(s1<=s2&&a[i]<=a[v[s2]]) s2--;
        s2++;
v[s2]=i;
if(v[s1]==i-k){
        s1++;
}
if(i>=k){
    ans=ans+a[v[s1]];
}
}
cout<<ans<<endl;
}