#include <iostream>
#include <vector>
#include <iomanip>
//#include <chrono>
#include <map>
#include <string>
#include <set>
#include <algorithm>
#include <cmath>
#include <bits/stdc++.h>
using namespace std;
//using namespace chrono;
#define pb push_back
#define FastIO ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define F first
#define S second
typedef long long ll;
typedef vector< int > vi;
typedef vector< ll > V;
typedef map<int, int > mp;
#define debug cout << -1 << endl;
#define REP(i, a, b) for(int i=a; i<b; i++)
#define f0r(i, n) for (int i = 0; i < n; ++i)
#define fore(a, x) for (auto& a : x)
#define fori(i, a, b) for (int i = (a); i < (b); ++i)
//#define pop pop_back
#define sz(a) (int)a.size()
//#define fin cin
//#define fout cout
const ll MOD = 1000000007;
const int INF = (int)1e9;
int dx[] = {-1, 0, 1, -1, 1, -1, 0, 1};
int dy[] = {-1, -1, -1, 0, 0, 1, 1, 1};
const double PI = acos(-1.0);
const double diff = 1e-6;
void solve()
{
int n, k;
cin >> n >> k;
vi v(n), v2;
ll ans;
f0r(i, n) {
cin >> v[i];
if(i) v2.pb(v[i]-(v[i-1]+1));
}
ans = v[n-1]+1-(v[0]);
sort(v2.begin(), v2.end());
reverse(v2.begin(), v2.end());
for(int i=0; i<k-1; i++) {
ans -= v2[i];
}
cout << ans << "\n";
}
int main()
{
//FastIO;
//freopen("maxcross.in", "r", stdin);
//freopen("maxcross.out", "w", stdout);
//ofstream fout ("wormhole.out");
//ifstream fin ("wormhole.in");
int t;
t = 1;
// cin >> t;
while(t--) {
solve();
}
}
