#include<fstream>
using namespace std;
typedef long long ll;
ifstream in("deque.in");
ofstream out("deque.out");

const int Nmax = 5000001;
int d[Nmax],st=1,dr;
int v[Nmax],N,K,x;
ll s;

int main(){
    in>>N>>K;
    for(int i=1;i<=N;i++) in>>v[i];
    for(int i=1;i<=N;i++){
        while(st<=dr && d[st]<=i-K) st++;
        while(st<=dr && v[d[dr]]>v[i]) dr--;
        d[++dr]=i;
        if(i>=K) s+=v[d[st]];
    }
    out<<s<<'\n';
    return 0;
}