#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define MP make_pair
#define PB push_back
using ll = long long;
using ld = long double;
using pi = pair<int, int>;
using pll = pair<ll, ll>;
template<typename T>
using vec = vector<T>;
template<typename T, int N>
using arr = array<T, N>;
ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
const int INF = 1e9 + 7;
const int MOD = 998244353;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int N, K;
cin >> N >> K;
vec<int> T(N + 1);
vec<int> v;
for (int i = 1; i <= N; i++)
{
cin >> T[i];
if (i > 1) v.PB(T[i] - T[i - 1] - 1);
}
sort(v.begin(), v.end());
int k = N;
int idx = 0;
int ans = N;
while (k > K)
{
ans += v[idx++];
k--;
}
cout << ans << '\n';
}
