#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define ll long long
#define ull unsigned long long
#define ld long double
#define pll pair<ll, ll>
#define pii pair<int, int>
#define coutpair(p) cout << p.first << " " << p.second << "|"
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T> using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll n, k; cin >> n >> k;
ll t[n];
for (int i=0; i<n; i++) cin >> t[i];
vector<ll> v;
for (int i=1; i<n; i++) v.push_back(t[i]-t[i-1]);
sort(v.begin(), v.end(), greater<ll>());
ll ans = t[n-1]+1-t[0];
for (int i=0; i<k-1; i++) ans -= v[i]-1;
cout << ans;
return 0;
}
