#include<iostream>
#include<algorithm>

using namespace std;

int main(){
   
    int input_num;
    cin >> input_num;
    int output_group_num;
    cin >> output_group_num;
    
    long input[input_num];
    for(int i=0;i<input_num;++i){
        cin >> input[i];
    }
    
    sort(input,input+input_num);
    
    long distance[input_num-1];
    for(int i=0;i<input_num-1;++i){
        distance[i] = input[i+1] - input[i];
    }
    
    sort(distance,distance+input_num-1);
    long output=0;
    for(int i=0;i<input_num-output_group_num;++i){
        output += distance[i];
    }
    
    cout << output << endl;
    return 0;
}