#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vii> vvii;
typedef vector<vi> vvi;
typedef pair<double, double> dodo;
#define pb(x) push_back(x)
#define mp(x, y) make_pair(x, y)
int N, K;
int arr[100000];
int main(int argc, char **argv) {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> N >> K;
for (int i = 0; i < N; i++) {
cin >> arr[i];
}
multiset<int> MS;
for (int i = 0; i < N-1; i++) {
MS.insert(arr[i+1] - arr[i] - 1);
}
K = N-K;
int ans = N;
while (K--) {
ans += *MS.begin();
MS.erase(MS.begin());
}
cout << ans << endl;
return 0;
}
