#include <bits/stdc++.h>
using namespace std;
#define int long long
#define run ios_base::sync_with_stdio(0);cin.tie(0);
#define F first
#define S second
#define endl '\n'
const int inf = 1e18+7;
const int sz = 1e5+5;
void solve() {
int m,k;
cin >> m >> k;
int a[m+1];
vector<int>diff;
for(int i=1; i <= m;i++) cin >> a[i];
vector<int>t;
for(int i = 1; i <= m;i++){
t.push_back(a[i]);
}
k--;
for(int i=1; i < t.size();i++){
diff.push_back(abs(t[i] - t[i-1]) - 1);
}
sort(diff.begin(),diff.end());
reverse(diff.begin(),diff.end());
int cost = 0;
for(int i = 0;i < diff.size() & k > 0;i++){
cost+=diff[i];
k--;
}
sort(a+1,a+m+1);
int time = a[m] - a[1] + 1;
cout << time - cost << endl;
}
signed main() {
run;
int t = 1;
//cin >> t;
while (t--) {
solve();
}
}
// 11111100000
