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

int compare(const void *x, const void *y)
{
	if (*(long*)x > *(long*)y) return 1;
	else if (*(long*)x < *(long*)y) return -1;
	else return 0;
}

int main(void)
{
	int N, K, i;
	long a[50000], ans = 0, tmp[49999];
	scanf("%d%d", &N, &K);
	for (i = 0; i < N; ++i) scanf("%ld", &a[i]);
	qsort(a, N, sizeof(long), compare);
	for (i = 0; i < N - 1; ++i) tmp[i] = a[i + 1] - a[i];
	qsort(tmp, N - 1, sizeof(long), compare);
	for (i = 0; i < N - K; ++i) ans += tmp[i];
	printf("%ld", ans);
	return 0;
}