#include<fstream>
#include<iostream>
#include<stack>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int dq[5000001];
int main(){
    int n, k, j, i, ul = 0, pr = 1, x, minim = 0;
    int suma = 0;
    fin >> n >> k;
    for(int i=1;i<=n;i++){
        fin>>x;
        dq[++ul]=x;
        if(i>=k){
            minim=dq[pr];
            for(j=pr+1;j<=ul;j++)
                if(dq[j]<minim)minim=dq[j];
            suma+=minim;
            pr++;
        }
    }
    fout << suma;
    return 0;
}