#include <bits/stdc++.h>
using namespace std;
// #define int ll
#define MAX LLONG_MAX
#define st first
#define nd second
#define endl '\n'
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(), x.end()
typedef long long ll;
typedef pair< int, int > ii;
typedef pair< int, ii > iii;
typedef vector< int > vi;
typedef vector< ii > vii;
typedef vector< iii > viii;
typedef vector< vi > vvi;
typedef vector< vii > vvii;
typedef vector< viii > vviii;
const int N = 1e5 + 5;
int a[N];
priority_queue<int, vi, greater<int>> q;
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, k; cin >> n >> k;
for(int i=1; i<=n; i++) cin >> a[i];
for(int i=2; i<=n; i++) q.push(a[i] - a[i-1] - 1);
int match = n, ans = n;
while(match > k){
auto mini = q.top(); q.pop();
match--;
ans += mini;
}
cout << ans;
}
