#include <bits/stdc++.h>
using namespace std;
#define int long long int
#define MP make_pair
#define pb push_back
#define REP(i,n) for(int (i) = 0; (i) < (n); (i)++)
void fastio() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
}
const double EPS = 0.00001;
const int INF = 1e17+500;
const int N = 1e5+5;
const int M = 3e5+5;
const int ALPH = 26;
const int LGN = 25;
const int MOD = 1e9+7;
int n,k;
vector<int> t;
vector<int> itrs;
inline void solve() {
cin>>n>>k;
t.resize(n);
for(int i = 0; i<n; i++) {
cin>>t[i];
}
sort(t.begin(), t.end());
int tot = t.back() + 1 - t[0];
for(int i = 1 ;i<n; i++) {
itrs.pb(t[i] - t[i-1] - 1);
}
sort(itrs.begin(), itrs.end());
for(int i = 0; i<k-1; i++) {
tot -= itrs.back();
itrs.pop_back();
}
cout<<tot<<"\n";
}
signed main() {
fastio();
int test = 1;
//cin>>test;
while(test--) {
solve();
}
}
