#include <bits/stdc++.h>
using namespace std;
#define int long long
void solve() {
vector<pair<int, int>> vt;
int n, k;
cin >> n >> k;
int a[n + 1];
for(int i = 1; i <= n; i++) {
cin >> a[i];
}
for(int i = 1; i < n; i++) {
vt.push_back({a[i + 1] - a[i], i});
}
vector<int> e;
sort(vt.rbegin(), vt.rend());
for(int i = 0; i < k - 1; i++) {
e.push_back(vt[i].second);
}
int ans = 0;
e.push_back(0);
e.push_back(n);
sort(e.begin(), e.end());
for(int i = 1; i < e.size(); i++) {
int idx = e[i];
int idx2 = e[i - 1] + 1;
ans += (a[idx] - a[idx2] + 1);
}
cout << ans << endl;
}
signed main() {
int t = 1;
//cin >> t;
while (t--) {
solve();
}
}
