#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define int long long
const int MOD = 1e9 + 7;
const int INF = 1e15;
const int N = 1e6;
int n, m, k, a, b, c, d, h, l, r, q, u, v, x, y;
vector<int> arr(N);
void solve() {
cin >> n >> k;
vector<int> gaps;
h = 0;
m = 1;
c = 0;
cin >> arr[1];
for(int i = 2; i<=n; i++) {
cin >> arr[i];
if(arr[i] > arr[i-1] + 1) {
gaps.pb(arr[i]-arr[i-1]-1);
c += m;
m = 1;
h++;
}
else {
m++;
}
}
c += m;
h++;
if(k>=h) {
cout << c; return;
}
sort(gaps.begin(), gaps.end());
// cout << c << " ";
for(int i = 0; i<h-k; i++) {
c += gaps[i];
// cout << gaps[i] << " ";
}
cout << c;
}
int32_t main() {
ios::sync_with_stdio(false);
cout.tie(0); cin.tie(0);
int tc = 1;
// cin >> tc;
while(tc--) {
solve();
cout << "\n";
}
return 0;
}
