#include <fstream>

using namespace std;
ifstream f ("deque.in");
ofstream g ("deque.out");

int v[100],i,n,m;
int main()
{
    f>>n>>m;
    for(i=1;i<=n;i++)
        f>>v[i];
    int t=1,s=0;
    while(m<=n)
    {
        int mn=99999;
        for(i=t;i<=m;i++){if(mn>v[i])mn=v[i];}

        s=s+mn;
        t++;
        m++;
    }
    g<<s<<" ";

    return 0;
}