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