#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")
#define McQueen ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define rep(i , a , n) for(int i = a; i < n; i++)
#define scan(a) for(auto & x : a) cin >> x;
#define rall(a) a.rbegin(), a.rend()
#define all(a) a.begin(), a.end()
#define double long double
#define int long long
using ll = long long;
using pii = pair<int , int>;
using ull = unsigned long long;
using vvi = vector<vector<int>>;
using vvc = vector<vector<char>>;
const ll mod = 1e9 + 7 , LOG = 20 , INF = 1e18 , N = 1e5 + 5 , K = 1 << 20;
ll gcd(ll a, ll b) {
return b == 0 ? a : gcd(b, a % b);
}
struct SegmentTree{
int n;
vector<int> der;
void build(vector<int> & a , int v , int l , int r){
if(r - l == 1){
if(l < (ll)a.size()) der[v] = a[l];
return;
}
int mid = (l + r) >> 1;
build(a , v * 2 + 1 , l , mid);
build(a , v * 2 + 2 , mid , r);
der[v] = der[v * 2 + 1] + der[v * 2 + 2];
}
SegmentTree(vector<int> & a){
n = 1;
while(n < (ll)a.size()) n <<= 1;
der.assign(n * 2 - 1 , 0LL);
build(a , 0 , 0 , n);
};
void update(int v , int l , int r , int i , int val){
if(r - l == 1){
der[v] = val;
return;
}
int mid = (l + r) >> 1;
if(i < mid) update(v * 2 + 1 , l , mid , i , val);
else update(v * 2 + 2 , mid , r , i , val);
der[v] = der[v * 2 + 1] + der[v * 2 + 2];
}
void update(int i , int val){
update(0 , 0 , n , i , val);
}
int get(int v , int l , int r , int ql , int qr){
if(l >= qr or r <= ql) return 0LL;
if(l >= ql and r >= qr) return der[v];
int mid = (l + r) >> 1;
int x = get(v * 2 + 1 , l , mid , ql , qr);
int y = get(v * 2 + 2 , mid , r , ql , qr);
return x + y;
}
int get(int ql , int qr){
return get(0 , 0 , n , ql , qr);
}
};
struct SegmentTree1 {
int n;
vector<int> der;
void build(vector<int> & a , int v , int l , int r){
if(r - l == 1){
if(l < (ll)a.size()) der[v] = a[l];
return;
}
int mid = (l + r) >> 1;
build(a , v * 2 + 1 , l , mid);
build(a , v * 2 + 2 , mid , r);
der[v] = max(der[v * 2 + 1] , der[v * 2 + 2]);
}
SegmentTree1(vector<int> & a){
n = 1;
while(n < (ll)a.size()) n <<= 1;
der.assign(n * 2 - 1 , -INF);
build(a , 0 , 0 , n);
};
void update(int v , int l , int r , int i , int val){
if(r - l == 1) {
der[v] = val;
return;
}
int mid = (l + r) >> 1;
if(i < mid) update(v * 2 + 1 , l , mid , i , val);
else update(v * 2 + 2 , mid , r , i , val);
der[v] = max(der[v * 2 + 1] , der[v * 2 + 2]);
}
void update(int i , int val){
update(0 , 0 , n , i , val);
}
int get(int v , int l , int r , int ql , int qr){
if(l >= qr or r <= ql) return -INF;
if(l >= ql and r <= qr) return der[v];
int mid = (l + r) >> 1;
int x = get(v * 2 + 1 , l , mid , ql , qr);
int y = get(v * 2 + 2 , mid , r , ql , qr);
return max(x , y);
}
int get(int ql , int qr) {
return get(0 , 0 , n , ql , qr);
}
};
int a[N],b[N];
inline void solve(){
int n , k;
cin >> n >> k;
for(int i = 0; i < n; i++){
cin >> a[i];
if(i > 0) b[i - 1] = a[i] - a[i - 1] - 1;
}
sort(b , b + n - 1);
int ans = n;
for(int i = 0; i < n - k; i++){
ans += b[i];
}
cout << ans << "\n";
}
signed main(){
//freopen("gcm.in", "r", stdin); freopen("gcm.out", "w", stdout);
McQueen;
int tt = 1;
//cin >> tt;
while(tt--) {
solve();
}
return 0;
}
