#include <bits/stdc++.h>
#include <iostream>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update> order_set;
mt19937 mt_rand(chrono::high_resolution_clock::now().time_since_epoch().count());
//uniform_int_distribution<int> gen(-1e9, 1e8); ///(min, max)
//int random() {return gen(mt_rand);}
const int mxN = 1e6+50000;
const int mod = 998244353;
const int mxlogN = 34;
const int mxK = 26;
const int inf = 1e9;
const int K = 100000;
int a[mxN];
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, k; cin >> n >> k;
for(int i=0; i<n; i++) cin >> a[i];
vector<int> b;
for(int i=1; i<n; i++) b.push_back(a[i]-a[i-1]-1);
sort(b.begin(), b.end());
ll cost=a[n-1]-a[0]+1;
while(--k&&b.size())
{
cost-=b.back();
b.pop_back();
}
cout << cost << "\n";
}
/**
1 2 3 4 5 6
*/
