#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque < int > v;
int n,k,x,mn,i;
long long sum;
int main()
{
    f>>n>>k;
    f>>x;
    mn=x;
    v.push_back(x);
    for(i=2;i<=k;i++)
    {
        f>>x;
        if(x<mn) mn=x;
        v.push_back(x);
    }
    sum+=mn;
    for(;i<=n;i++)
    {
        f>>x;
        v.pop_front();
        v.push_back(x);
        int l=v.size();
        mn=v.at(0);
        for(int p=1; p<l; p++)
            if(v.at(p)<mn) mn=v.at(p);
        sum+=mn;

    }
    g<<sum;
    return 0;
}