#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

int main() {
	int v[100], n, k;
	fin >> n;
	fin >> k;
	for (int i = 0; i < n; i++)
		fin >> v[i];
	int f[100];
	int x = 0;
	int s = 0;
	while (k <= n) {
		int minim = v[x];
		for (int i = x; i < k; i++)
			if (minim > v[i])
				minim = v[i];
		s += minim;
		++x;
		++k;
		
	}
	fout << s;
	return 0;
}