#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
using ll = long long;
#define all(x) x.begin(), x.end()
#define oset tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update>
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
//ifstream cin("cycle2.in");
//ofstream cout("cycle2.out");
ll n, k; cin >> n >> k;
vector<ll> a(n);
vector<ll> b(n);
for(int i = 0; i < n; i++){
cin >> a[i];
}
for(int i = n-1; i >= 1; i--){
b[i] = a[i] - a[i-1] - 1;
}
sort(b.rbegin(), b.rend());
ll ans = a[n-1] - a[0] + 1;
for(int i = 0; i < k-1; i++){
ans -= b[i];
}
cout << ans << '\n';
}
