#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>


int main()
{
	FILE* in = fopen("deque.in", "r");
	if (in == NULL)
	{
		printf("Eroare la formarea fisierului DEQUE.IN");
		return 1;
	}
	FILE* out = fopen("deque.out", "w");

	int n, k;
	fscanf(in, "%d", &n);
	fscanf(in, "%d", &k);
	int* v = (int*)malloc(sizeof(int) * n);
	for (int i = 0;i < n;i++)
		fscanf(in, "%d", &v[i]);

	
	int suma=0;


	for (int i = 0;i <= n-k;i++)
	{
		int min = v[i];
		for (int j = i;j < i + k;j++)
		{
			if (v[j] < min)
				min = v[j];
		}
		suma = suma + min;
	}
	
	fprintf(out,"%d", suma);
}