#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 2e5 + 2;
const int M = 5e5 + 2;
int mod = 1000000007;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, k;
cin >> n >> k;
vector<int> a(n);
for (int i = 0; i < n; i++) cin >> a[i];
vector<int> b;
for (int i = 1; i < n; i++) b.push_back(a[i] - a[i - 1] - 1);
sort(b.rbegin(), b.rend());
int ans = a.back() + 1 - a[0];
for (int i = 0; i < k - 1; i++) ans -= b[i];
cout << ans << en;
return 0;
}
