#include<bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
ifstream fin("deque.in"); ofstream fout("deque.out");



int n, t, q, k, l, a[5000005];








int main(){
fin>>n>>k;

ll sum=0;

vector<int> s;

for(int i=1; i<=n; i++){
    int x; fin>>x;
    a[i]=x;
    while(s.size()>=1 && a[s[s.size()-1] ]>a[i] ){s.pop_back();}
    s.pb(i);
if( (i-k+1) >=s[0]  ){sum+=a[s[0]];  s.erase(s.begin(), s.begin()+1);}



}
sum+=a[s[0] ];
fout<<sum;


return 0;
}