#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define sz(v) (int)v.size()
#define MOO(i, a, b) for(int i=a; i<b; i++)
#define M00(i, a) for(int i=0; i<a; i++)
#define MOOd(i,a,b) for(int i = (b)-1; i >= a; i--)
#define M00d(i,a) for(int i = (a)-1; i>=0; i--)
#define FAST ios::sync_with_stdio(0); cin.tie(0);
#define finish(x) return cout << x << '\n', 0;
#define dbg(x) cerr << ">>> " << #x << " = " << x << "\n";
#define _ << " _ " <<
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int,int> pi;
typedef pair<ld,ld> pd;
typedef complex<ld> cd;
const int MAX_N = 100100;
int n, k;
ll arr[MAX_N];
int main() { FAST
cin >> n >> k;
M00(i, n) cin >> arr[i];
sort(arr, arr+n);
ll tot = arr[n-1]-arr[0]+1;
vector<ll> diffs(n-1);
M00(i, n-1) {
diffs[i] = arr[i+1] - arr[i] - 1;
}
sort(all(diffs));
reverse(all(diffs));
M00(i, k-1) {
tot -= diffs[i];
}
finish(tot);
}
