#include <bits/stdc++.h>
#define ll long long
#define f(i, a, b) for(ll i = a; i <= b; ++i)
#define ff(i, a, b) for(ll i = a; i < b; ++i)
#define F(i, a, b) for(ll i = a; i >= b; --i)
#define FF(i, a, b) for(ll i = a; i > b; --i)
#define x first
#define y second
#define X real()
#define Y imag()
using namespace std;
typedef complex<ll> P;
typedef pair<ll, ll> ii;
typedef tuple<ll, ll, ll> iii;
const ll N = 1e5+7;
ll n, m, ans = 0, a[N];
vector<ll> arr;
signed main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n >> m;
f(i,1,n){
cin >> a[i];
}
ans += n;
sort(a+1, a+1+n);
ff(i,1,n){
arr.push_back(a[i+1] - a[i] - 1);
ans += a[i+1] - a[i] - 1;
}
sort(arr.begin(), arr.end(), less<ll>());
m-=1;
while(m && arr.size()){
ans -= arr.back();
m--;
arr.pop_back();
}
cout << ans;
}
