// 23 - 12 - 23
#include<bits/stdc++.h>
using namespace std;
#define read() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define day() time_t now = time(0);char* x = ctime(&now);cerr<<"Right Now Is : "<<x<<"\n"
#define ii pair<int,int>
#define X first
#define Y second
const long long MAX = (int)1e5 + 5;
const long long INF = (int)1e9;
const long long MOD = (int)1e9 + 7;
int n,k;
int a[MAX];
signed main(){
read();
cin >> n >> k;
vector<int> rt;
for(int i = 1;i <= n;i++){
cin >> a[i];
if(i > 1)rt.push_back(a[i] - a[i - 1] - 1);
}
int ans = n;
sort(rt.begin(),rt.end());
for(int i = 0;i < n - k;i++)ans += rt[i];
cout << ans;
}
