#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
#define pb push_back
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define N 100005
#define INF 0x3f3f3f3f
#define MOD 1000000007LL
int a[N];
vector<int> v;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, k;
cin>>n>>k;
int res = n;
for(int i = 1; i <= n; i++)
cin>>a[i];
for(int i = 2; i <= n; i++)
v.push_back(a[i] - a[i - 1] - 1);
sort(v.begin(), v.end());
k = n - k;
for(int i = 0; i < k; i++)
res += v[i];
cout<<res;
}
