#include <stdio.h>
#include <stdlib.h>
#include <string.h>


int minPos(int* array, int start, int end) {
	int min = array[start];
	int result = start;
	for (int i=start+1; i < end; i++) {
		if (min > array[i]) {
			min = array[i];
			result = i;
		}
	}
	return result; 
}

int maxPos(int* array, int start, int end) {
	int max = array[start];
	int result = start;
	for (int i=start+1; i < end; i++) {
		if (max < array[i]) {
			max = array[i];
			result = i;
		}
	}
	return result;
}

void printArray(int* array, int n) {
	printf("\n");
	for (int j=0; j< n; j++)
		printf("%d ", array[j]);
	printf("\n");
}

int main(int argc, char** argv) {
	FILE *fin = fopen("input.txt", "r");
	
	int n,k;
	fscanf(fin, "%d ", &n);
 	fscanf(fin, "%d\n", &k);
	
	int temp;
	int* vett = (int*) malloc(n*sizeof(int));
	int* vettScan = (int*) malloc((n+1)*sizeof(int));
	for (int i=0; i< n; i++) {
		fscanf(fin, "%d ", &temp);
		vett[i] = temp;
	}
	fclose(fin);

	//printArray(vett, n);

	vettScan[0] = 0;			// temp = (vettScan[i] = temp + vett[i-1])
	for (int i=1; i < n+1; i++)
		vettScan[i] = vettScan[i-1] + vett[i-1];

	//printArray(vettScan, n+1); 

	int min = minPos(vettScan, 0, n - k); 
	int max = maxPos(vettScan, min, n);

	int result = vettScan[max] - vettScan[min];
	
	//printf("\n   %d\n", result);
	FILE *fout = fopen("output.txt", "w");
	fprintf(fout, "%d", result);
	fclose(fout);
}