#include "bits/stdc++.h"
#define int unsigned long long
#define all(v) v.begin() , v.end()
#define rall(v) v.rbegin() , v.rend()
#define pii pair<int , int>
#define pb push_back
#define F first
#define S second
using namespace std;
const int N = 1e5 + 5;
const int mod = 1e9 + 7;
const int inf = 1e18;
void Yusiff(){
int n , k; cin >> n >> k;
int a[n + 1];
for(int i = 0; i < n; i++){
cin >> a[i];
}
if(n <= k){
cout << n << '\n';
}
vector<array<int , 3>> arr;
for(int i = 1; i < n; i++){
int diff = a[i] - a[i - 1];
arr.pb({diff , i - 1 , i});
}
sort(all(arr));
int m = n - k;
int sum = k;
for(int i = 0; i < m; i++){
sum += arr[i][0];
}
cout << sum << '\n';
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
// freopen("wormsort.in", "r", stdin);
// freopen("wormsort.out", "w", stdout);
int T = 1;
// cin >> T;
while(T--){
Yusiff();
}
}
/*
*/
