#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-O3")
#pragma GCC target("avx2")
using namespace std;
#define pb push_back
#define sz size()
#define all(x) x.begin(), x.end()
#define F first
#define S second
typedef pair < int, int > pii;
typedef vector < int > vi;
typedef vector < vi > vvi;
void solve(){
int n, k;
cin >> n >> k;
int a[n + 7];
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
multiset <int> s;
for (int i = 2; i <= n; i++) {
int diff = a[i] - a[i - 1];
s.insert(diff - 1);
}
k--;
while (s.sz > 0 && k > 0) {
s.erase(--s.end());
k--;
}
int ans = 0;
for (auto i : s) {
// cout << i << " ";
ans += i;
}
ans += n;
cout << ans;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int t = 1;
// cin >> t;
while (t--) {
solve();
cout << "\n";
}
}
