#include <fstream>

using namespace std;

int v[5000000], d[5000000], f=1, e=0, n, k;
long long sum=0;
int main()
{

    ifstream in("deque.in");
    in>>n>>k;

    for(int i=0;i<n;i++){
        in>>v[i];

        while(f <= e && v[d[e]]>v[i]) e--;
        d[++e] = i;
        if(i-d[f]+1>k)f++;
        if(i>=k-1)sum+=v[d[f]];
    }

    ofstream out("deque.out");
    out<<sum;
    return 0;
}