#include <fstream>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int i, j, n, m, k, st, dr;
int d[5000002];
int v[5000002];
long long s;
int main(){
    cin>>n>>k;
    cin>>v[1];
    st=1;
    dr=1;
    d[1]=1;
    for(i=2;i<=n;i++){
        cin>>v[i];
        while(st<=dr && v[d[dr]]>v[i])
            dr--;
        d[++dr]=i;
        if(i-k+1>d[st])
            st++;
        if(i>=k)
            s+=v[d[st]];
    }
    cout<<s;



}