#include "bits/stdc++.h"
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
using i32 = int;
using u32 = unsigned;
using i16 = short;
using u16 = unsigned short;
using ld = long double;
using ii = pair<int, int>;
void solve() {
int n, k;
i64 ans = 0;
cin >> n >> k;
vector<int> a(n);
priority_queue<int> pq;
for(int& v : a) cin >> v;
for(int i = 1; i < n; ++i) pq.push(-a[i] + a[i - 1]);
while(n > k) {
int t = -pq.top();
pq.pop();
ans += t;
--n;
}
cout << ans + k << '\n';
}
int main() {
ios_base :: sync_with_stdio(false);
cin.tie(0);
int t = 1;
//cin >> t;
while(t--) solve();
return 0;
}
