// yukicoder: No.615 集合に分けよう
// 2019.5.11 bal4u

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

//// 高速入力
#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

long long in()    // 非負整数の入力
{
	long long n = 0; int c = gc();
	do n = 10 * n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}

long long a[50005], d[50005];

int cmp(const void *a, const void *b) {
	long long t = *(long long *)a - *(long long *)b;
	if (t < 0) return -1;
	return t > 0;
}
 
int main()
{
	int i, N, K;
	long long ans;
	
	N = (int)in(), K = (int)in();
	for (i = 0; i < N; i++) a[i] = in();
	qsort(a, N, sizeof(long long), cmp);
	for (i = 1; i < N; i++) d[i] = a[i] - a[i-1];
	qsort(d+1, N-1, sizeof(long long), cmp);
	ans = 0; for (i = N-K; i > 0; i--) ans += d[i];
	printf("%lld\n", ans);
	return 0;
}