#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <set>
#include <map>
#include <string.h>
#include <cmath>

using namespace std;
typedef long long i64;
typedef long double ld;
typedef pair<i64,i64> P;
#define rep(i,s,e) for(int (i) = (s);(i) <= (e);++(i))

int n;
int k;
i64 a[101010];

int main()
{
	cin >> n >> k;
	rep(i,0,n - 1) cin >> a[i];
	sort(a,a + n);
	vector<i64> vec;
	rep(i,1,n - 1)
		vec.push_back(a[i] - a[i - 1]);
	sort(vec.begin(),vec.end());
	i64 result = 0;
	rep(i,1,n - k)
		result += vec[i - 1];
	cout << result << endl;
}