#include <iostream>
#include <fstream>
#define inf 5000000
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int st,dr=1,n,k,i;
long long s;
int d[inf],v[inf];
int main(){
   fin>>n>>k;
    for(i=1;i<=n;i++){
      fin>>v[i];
        while(st<=dr&&v[i]<=v[d[dr]])
            dr--;
        d[++dr]=i;
        if(d[st]+k==i)
            st++;
        if(i>=k)
            s+=v[d[st]];
    }
 fout<<s;
}