/*
STATEMENT: NONE
FILE: main.cpp
AUTHOR: Win [Discord: @un.de.fined, Github: https://github.com/Winzzwz]
TIME: 3/31/2026, 8:32:15 AM
LANG: C++
*/
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void dbg() { cout << "\n"; }
template<typename H, typename... T>
void dbg(H h, T... t) {
cout << h << " ";
dbg(t...);
}
#define int long long
#define pii pair<int,int>
const int N = 1e5+10;
int a[N];
vector<int> v;
int32_t main() {
cin.tie(0)->sync_with_stdio(0);
int n,k; cin >> n >> k;
int ans = 0;
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]);
sort(v.begin(),v.end(),greater<int>());
ans = a[n]-a[1]+1;
for (int i = 1; i < k; i++) {
ans -= v[i-1]-1;
}
cout << ans;
return 0;
}
