/**
____ ____ ____ ____ ____
||a |||t |||o |||d |||o ||
||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|
**/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main () {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int N, K;
cin >> N >> K;
int T[N];
for (int i = 0; i < N; i++) {
cin >> T[i];
}
vector <int> diff;
for (int i = 0; i + 1 < N; i++) {
diff.push_back(T[i + 1] - T[i] - 1);
}
sort(diff.begin(), diff.end(), greater <int> ());
int answer = T[N - 1] - T[0] + 1;
for (int i = 0; i < min(K - 1, (int) diff.size()); i++) {
answer -= diff[i];
}
cout << answer << "\n";
return 0;
}
