#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    
    int N, K;
    cin >> N >> K;
    
    vector<long long> A(N);
    vector<long long> B(N-1);
    for ( int i = 0; i < N; i++ ) {
        cin >> A[i];
    }
    
    sort( A.begin(), A.end() );
    
    for ( int i = 1; i < N; i++ ) {
        B[i-1] = A[i] - A[i-1];
    }
    sort( B.begin(), B.end(), greater<long long>() );
    
    long long ans = 0;
    for ( int i = K-1; i < N-1; i++ ) {
        ans += B[i];
    }
    
    cout << ans << endl;
    
    return 0;
}