#include <iostream>
#include <algorithm>
#include <stack>
#include <vector>
#include <set>
#include <cstring>
#include <queue>
#include <map>
#include <cmath>
#define aldgebu return
#define ff first
#define sc second
#define pb push_back
#define pii pair <int,int>
#define p push
#define ll long long
#define pll pair<ll, ll>
#define Nptr nullptr
using namespace std;
const ll inf = 1e9;
const ll mod = 1000000000 + 7;
void Dontfuckedup(){
int N, K;
cin >> N >> K;
vector <int> v;
int prev, cur;
cin >> prev;
for (int i = 2; i <= N; i++){
cin >> cur;
v.pb(cur - prev);
prev = cur;
}
sort(v.begin(), v.end());
ll ans = N;
for (int i = 0; i < N - K; i++){
ans += v[i] - 1;
}
cout << ans;
}
int32_t main () {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int T = 1; //cin>>T;
while (T--)Dontfuckedup();
return 0;
}
