#include <bits/stdc++.h>
#define int long long
#define pii pair<int, int>
#define vc vector
#define Fin(a) for (auto& i : a)
#define fih ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
//#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
using namespace std;
signed main() {
fih
int n, k;
cin >> n >> k;
vector<int> input(n);
for (int i = 0;i < n;i++) cin >> input[i];
int mm = input[n-1] - input[0] + 1;
vc<int> bos;
for (int i = 0;i < n-1;i++) {
bos.pb(input[i+1] - input[i] - 1);
}
sort(bos.begin(), bos.end());
while (--k && bos.size() > 0) {
mm -= bos.back();
bos.pop_back();
}
cout << mm << "\n";
}
