#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define pb push_back
#define ss second
#define ff first
#define vt vector
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, int> pdi;
const int inf = 1e9 + 10000;
const int mod = 1e9+7;
const int maxn = 5e5 + 12;
void solve() {
int n, k;
cin >> n >> k;
int t[n], p[n];
k = n - k;
int ans = n;
for(int i = 0; i < n; i++) {
cin >> t[i];
if(i)p[i] = t[i] - t[i - 1] - 1;
}
sort(p + 1, p + n);
for(int i = 1; i <= k; i++) {
ans += p[i];
}
cout << ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int times = 1;
//cin >> times;
for(int i = 1; i <= times; i++) {
solve();
}
return 0;
}
