#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> ii;
#define int long long
signed main() {
int n, k;
cin >> n >> k;
vector<int> t(n, 0);
priority_queue<ii> diff;
for (int i = 0; i < n; ++i) {
cin >> t[i];
if (i > 0) {
diff.push(ii(t[i] - t[i - 1], i - 1));
}
}
priority_queue<int, vector<int>, greater<int>> splits;
for (int i = 0; i < k - 1; ++i) {
splits.push(diff.top().second);
//cout << diff.top().second << '\n';
diff.pop();
}
int sum = 0;
int prev_ind = 0;
while (!splits.empty()) {
int i = splits.top();
splits.pop();
sum += t[i] + 1 - t[prev_ind];
prev_ind = i + 1;
}
sum += t[n - 1] + 1 - t[prev_ind];
cout << sum << '\n';
}
