#include <iostream>
#include <algorithm>
using namespace std;

int main(){
    int N, K;
    cin >> N >> K;
    long nums[N];
    for(int i = 0; i < N; i++){
        cin >> nums[i];
    }
    sort(nums, nums + N);
    long differences[N - 1];
    for(int i = 0; i < N - 1; i++){
        differences[i] = nums[i + 1] - nums[i];
    }
    sort(differences, differences + N - 1);
    long ans = 0;
    for(int i = 0; i < N - K; i++){
        ans += differences[i];
    }
    cout << ans << endl;
}