#include <fstream>
#include <vector>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long long S;
int main()
{
    vector <long long> v;
    long long N,K,i,j,x;
    f>>N>>K;
    for(i=0;i<N;++i){
        f>>x;
        v.push_back(x);
    }
    long long p=K;
    for(i=0;i<=N-K;++i){
        long long minn=10000000;
        for(j=i;j<p;++j)
            if(v[j]<minn) minn=v[j];
        S+=minn;
        p++;
    }
    g<<S<<"\n";
    f.close();
    g.close();
    return 0;
}