// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <unordered_map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
using namespace std;
#define int long long
#define endl "\n"
#define fi first
#define se second
const int M=1e6+3;
const int inf = 1e14;
const int LOG=18;
const int N=1e6+5;
int n , m , c , w , k , t=1 , q=1 , x , y , z , l , r;
void solve()
{
cin >> n >> k;
vector<int>a(n);
for (int i=0;i<n;i++){
cin >> a[i];
}
sort(a.begin(),a.end());
vector<int>b(n-1);
for (int i=0;i<n-1;i++){
b[i]=a[i+1]-a[i]-1;
}
sort(b.rbegin(),b.rend());
c=a[n-1]-a[0]+1;
k--;
for (int i=0;i<min(n-1,k);i++){
c-=b[i];
}
cout << c << endl;
}
signed main()
{
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);//DO NOT USE IN INTERACTIVE
cout << fixed << setprecision(9);
srand(time(0));
// int t=1;
// cin >> t;
for (int _=1;_<=t;_++){
solve();
q++;
}
}
