#include <bits/stdc++.h>
using namespace std;
const int N = 100005;
int n, m, k;
int a[N];
int b[N];
int main() {
  cin >> n >> m >> k;
  for (int i = 0; i < n; ++i) cin >> a[i];
  for (int i = 0; i < n - 1; ++i) {
    b[i] = a[i + 1] - a[i] - 1;
  }
  sort(b, b + n - 1);
  int kk = n;
  long long ans = n;
  for (int i = 0; i < n - 1; ++i) {
    if (kk == k) break;
    ans += b[i];
    kk--;
    if (kk == k) break;
  }
  cout << ans << endl;
  return 0;
}
