#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef map<int, int> mii;
typedef unordered_map<int, int> umii;
typedef map<ll, ll> mll;
typedef unordered_map<ll, ll> umll;
// struct Node
// {
// int node, len;
// Node() {node = len = 0;}
// Node(int node, int len) {this -> node = node, this -> len = len;}
// };
// typedef vector<Node> vg;
#define MAX 1000001
#define MOD 1000000007
#define fi first
#define se second
#define pf push_front
#define pb push_back
#define FOR(type, i, a, b) for(type i = (a); i <= (b); i++)
#define FORR(type, i, b, a) for(type i = (b); i >= (a); i--)
#define testBit(n, bit) ((n >> bit) & 1)
#define flipBit(n, bit) (n ^ (1ll << bit))
#define cntBit(n) __builtin_popcount(n)
#define cntBitll(n) __builtin_popcountll(n)
#define randomize mt19937_64 mt(chrono::steady_clock::now().time_since_epoch().count());
main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
int n, k; cin >> n >> k;
int a[n + 1];
int mi = INT32_MAX, ma = INT32_MIN;
FOR(int, i, 1, n){
cin >> a[i];
mi = min(mi, a[i]); ma = max(ma, a[i]);
}
int total = ma - mi + 1;
FOR(int, i, 1, n)
a[i] = a[i + 1] - a[i] - 1;
// FOR(int, i, 1, n - 1) cerr << a[i] << '|'; cerr << '\n';
sort(a + 1, a + n, greater<int>());
FOR(int, i, 1, k - 1) total -= a[i];
cout << total;
}
