// Muallif: Azimjon Mehmonali o'g'li
//=========================================================
// #pragma GCC optimize("Ofast")
// #pragma GCC target("avx,avx2,fma")
// #pragma GCC optimization ("unroll-loops")
//=========================================================
#ifdef DEBUG
#define xtp xtp1
#else
#define xtp(x)
#endif
//=========================================================
#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef unsigned long long ull;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
#define F first
#define S second
#define pb push_back
#define endl "\n"
#define ALL(a) (a).begin(), (a).end()
#define rALL(a) (a).rbegin(), (a).rend()
#define SORT(a) sort(ALL(a))
#define rSORT(a) sort(rALL(a))
#define REV(a) reverse(ALL(a))
#define sqr(x) ((x) * (x))
#define TEZ \
ios::sync_with_stdio(0); \
cin.tie(0);
const long double PI = 3.1415926535897;
const int mod = 1000000007LL;
const int INF = 1e18;
signed main() {
TEZ;
int n, k;
cin >> n >> k;
vi t(n);
for (int &i : t)
cin >> i;
int jv = t.back() - t[0] + 1;
vi b;
for (int i = 1; i < n; i++)
b.push_back(t[i] - t[i - 1] - 1);
rSORT(b);
for (int i = 0; i < k - 1; i++)
jv -= b[i];
cout << jv << endl;
return 0;
}
