#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
using namespace std;
#define int long long
#define nl '\n'
#define io ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
const int mod = 1000000007, mod2 = 998244353;
// change this
const int N = 100005;
int n, k, arr[N], ans;
vector<int> diff;
signed main() {
io;
cin >> n >> k;
ans = n;
for (int i=0; i<n; i++) {
cin >> arr[i];
if (i) diff.push_back(arr[i] - (arr[i-1]+1));
}
sort(diff.begin(), diff.end());
for (int i=0; i<n-k; i++) ans += diff[i];
cout << ans << nl;
}
