#include "bits/stdc++.h"
#include <algorithm>
using namespace std;
#ifndef debug
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#endif
#define int long long
#define all(x) (x).begin(), (x).end()
#define Tmp template<typename T>
#define len(x) ((int)((x).size()))
#define pii pair<int, int>
#define mii map <int, int>
#define yay cout<<"YES"
#define nay cout<<"NO"
#define X first
#define Y second
#define Q(x) return (void)(x)
Tmp using vec = vector<T>;
const int MOD = 1e9 + 7;
const int INF = LLONG_MAX;
const int BIG = 1e18;
const bool Tcases = 0;
void inits() {}
void solve() {
int n,k;
cin>>n>>k;
vec<int> a(n);
for(int &x:a)cin>>x;
sort(all(a));
vec<int> d; d.reserve(n);
for(int i=1;i<n;i++) d.push_back(a[i] - a[i-1] - 1);
sort(all(d)); reverse(all(d));
k=n-k;
while(k--&&d.size()) {
n += d.back(); d.pop_back();
}
cout<<n;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin.exceptions(cin.failbit);
#ifdef debug
freopen("input.txt", "r", stdin);
#endif
__builtin_ia32_ldmxcsr(40896);
inits();
int t=1;
if (Tcases) cin >> t;
for(; t--; solve(), cout << '\n') {
#ifdef debug
cout << "# "; // can be also used to print case numbers
cout.flush();
#endif
}
}
