#include<bits/stdc++.h>
#define X first
#define Y second
#define all(x) begin(x), end(x)
#define FOR(i, a, b) for(int i = (a); i <= (b); i++)
#define FORD(i, b, a) for(int i = (b); i >= (a); i--)
#define REP(i, a, b) for (int i = (a); i < (b); i++)
#define mxx max_element
#define mnn min_element
#define SQR(x) (1LL * (x) * (x))
#define MASK(i) (1LL << (i))
#define Point Vector
#define left Left
#define right Right
#define div Div
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
typedef pair<db, db> pdb;
typedef pair<ld, ld> pld;
typedef pair<int, int> pii;
typedef pair<int, pii> piii;
typedef pair<ll, ll> pll;
typedef pair<ll, pll> plll;
typedef pair<ll, int> pli;
typedef pair<ll, pii> plii;
template<class A, class B>
bool maximize(A& x, B y) {
if (x < y) return x = y, true; else return false;
}
template<class A, class B>
bool minimize(A& x, B y) {
if (x > y) return x = y, true; else return false;
}
/* END OF TEMPLATE */
const int N = 2e5 + 7;
int n, a[N], k;
int main() {
// freopen("test.inp", "r", stdin);
// freopen("test.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cin>>n>>k;
FOR(i, 1, n) cin>>a[i];
vector<pii> T;
int i = 1;
ll res = 0, ans = 0;
while (i <= n) {
int j = i;
while (j < n && a[j] + 1 == a[j + 1]) j++;
T.push_back({a[i], a[j]});
res+=a[j] - a[i] + 1;
ans++;
i = j + 1;
}
vector<int> A;
REP(i, 0, (int)T.size() - 1) A.push_back(T[i + 1].X - T[i].Y - 1);
sort(all(A));
for (auto x : A)
if (ans > k) res+=x, ans--;
cout<<res;
return 0;
}
