#include <iostream>
#include <fstream>
#include <queue>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int min(queue<int> x)
{   
    int min = x.front();
    while(!(x.empty()))
    {
        if(min > x.front())
            min = x.front();
        x.pop();
    }
    return min;
}   
int main()
{   
    queue<int> coada;
    int n,k,x,s = 0;
    f>>n>>k;
    while(coada.size() <k)
    {
        f>>x;
        coada.push(x);
    }
    s += min(coada);
    while(f>>x)
    {
        coada.push(x);
        coada.pop();
        s += min(coada);
    }
    g<<s;
    return 0;
}