#include<bits/stdc++.h>
#define rep(i,a,n) for (int i = a; i < n; i++)
#define per(i,n,a) for (int i = n - 1; i >= a; i--)
using namespace std;

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