#include <cstdio>
#include <iostream>
#include <vector>
#include <list>
#include <string>
#include <set>
#include <map>
#include <algorithm>
#include <fstream>
#include <cmath>
#include <queue>
#include <stack>
#include <cassert>
#include <cstring>
#include <climits>
#include <functional>
#include<cstdlib>
//#include "arc.h"
using namespace std;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef long long LL;
const int MAXN = 2e5 + 11;
using ll = long long;
typedef vector<int> lnum;
const int base = 1e9;
const ll mod1 = 1e9 + 7;
const ll mod2 = 1000000021;
const ll P = 31;
/*
void setIO(string name = "") {
cin.tie(0)->sync_with_stdio(0); // see /general/fast-io
if ((name.size())) {
freopen((name + ".in").c_str(), "r", stdin); // see /general/input-output
freopen((name + ".out").c_str(), "w", stdout);
}
}
*/
int n, k;
priority_queue<int> pq;
int a[MAXN];
int main()
{
cin.tie(0);
cout.tie(0);
ios_base::sync_with_stdio(false);
//setIO("time");
cin >> n >> k;
for (int i = 0; i < n; i++)
cin >> a[i];
int ans = a[n - 1] + 1 - a[0];
for (int i = 1; i < n; i++)
pq.push(a[i] - a[i - 1] - 1);
for (int i = 0; i < k-1 && pq.size(); i++)
{
int val = pq.top();
pq.pop();
ans -= val;
}
cout << ans << '\n';
return 0;
}
