#pragma GCC optimize("O3")
#pragma GCC target("avx")
#include <stdio.h>
// #include <vector>
#include <bits/stdc++.h>

using namespace std;
#define int long long
#define REP(i, n) for (int i = 0; i < (n); i++)
#define ALL(a) begin(a), end(a)
#define let const auto
int scan() {
  int result = 0;
  while (true) {
    auto k = getchar_unlocked();
    if (k < '0' || k > '9')
      break;
    else
      result = 10 * result + k - '0';
  }
  return result;
}
// let n = scan()
// let k = scan()
// let A = newSeqWith(n,scan()).sorted(cmp)
// let B = A.getNeignborDiff().sorted(cmp)
// echo B[0..<(n-k)].sum()
signed main() {
  let n = scan();
  let k = scan();
  vector<int> A(n);
  REP(i, n) A[i] = scan();
  sort(ALL(A));
  vector<int> B(n - 1);
  REP(i, n - 1) B[i] = A[i + 1] - A[i];
  sort(ALL(B));
  int ans = 0;
  REP(i, n - k) ans += B[i];
  printf("%d\n", ans);
}