#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MOD = 1000000007;
using pr = array<int, 2>;
signed main() {
int n, k; cin >> n >> k;
vector<int> vec(n);
for(int i = 0 ; i < n ; i++) cin >> vec[i];
sort(vec.begin(), vec.end());
vector<pr> s(n-1);
for(int i = 0 ; i < n-1 ; i++) {
s[i][0] = vec[i+1] - vec[i];
s[i][1] = i;
}
int r = vec[n-1] - vec[0] + 1;
sort(s.rbegin(), s.rend(), [](pr a, pr b) {return a[0] < b[0];});
for(int i = 0 ; i < k-1 and i < n ; i++) r -= s[i][0] - 1;
cout << r;
}
