#include<bits/stdc++.h>
#define fi first
#define se second
#define int long long
using namespace std;
using ll = long long;
using ii = pair<int, int>;
using aa = array<int,3>;
const int N = 2e5+5;
int n, k, res = 0;
int a[N];
priority_queue<int> pq;
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);cout.tie(NULL);
cin >> n >> k;
for (int i = 1; i <= n; i++){
cin >> a[i];
}
sort(a+1,a+1+n);
for (int i = 2; i <= n; i++) pq.push(a[i] - a[i-1]);
k--;
res -= k;
while (k--){
res += pq.top();
pq.pop();
}
cout << (a[n] + 1 - a[1]) - res;
return 0;
}
