#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
void solve() {
//write your code here...
int n, k, x = 0; cin >> n >> k;
vector<int> a(n), b;
for (auto &i : a) cin >> i;
for (int i = 0; i < n; i++) {
if (i == n - 1) x++;
else if (a[i + 1] != a[i] + 1) {
x++;
b.push_back(a[i + 1] - a[i] - 1);
}
}
if (k >= x) {cout << n << '\n'; return;}
x -= k;
sort(b.begin(), b.end());
for (int i = 0; i < x; i++) n += b[i];
cout << n << '\n';
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
ll T = 1;
//cin >> T;
while (T--) {
solve ();
}
return 0;
}
