#include <bits/stdc++.h>
using namespace std;
#define int long long
#define eb emplace_back
#define mp make_pair
#define pb push_back
#define pp pop_back
#define endl '\n'
#define ff first
#define ss second
#define stop exit(0)
#define sz(x) (int)x.size()
#define pause system("pause")
#define all(x) (x).begin(), (x).end()
#define deb(x) cout << #x << "-" << x << endl
mt19937 mt(time(nullptr));
typedef char chr;
typedef string str;
typedef long long ll;
typedef vector<int> vii;
typedef pair<int, int> pii;
const long long INF = LLONG_MAX;
const int inf = INT_MAX;
const int mod = 1000003;
const int MOD = 1000000007;
const int dx[] = {-1,0,1,0};
const int dy[] = {0,1,0,-1};
const double PI = 2 * acos(0.0);
const int N = 1e6+5;
int n,k,a[N];
vector <int> res;
inline void test_case() {
cin >> n >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
if (k >= n) {
cout << n << endl;
return;
}
for (int i = 1; i <= n; i++) {
if (i == n) continue;
res.pb(a[i+1]-a[i]-1);
}
sort(all(res),greater<int>());
int ans = a[n]-a[1]+1;
// deb(n-k-1);
for (int i = 0; i < k-1; i++) {
// deb(res[i]);
ans -= res[i];
}
cout << ans << endl;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int T = 1;
// cin >> T;
while (T--) test_case();
return 0;
}
