#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
const double eps = 1e-9;
const int mod = 1e9 + 7;
const int N = 1e3 + 5;
const int INF = 1e18;
signed main(){
fastio;
int n, k;
cin >> n >> k;
vector<int> v(n);
cin >> v[0];
vector<int> diff(n - 1);
for(int i = 0; i < n - 1; i++){
cin >> v[i + 1];
diff[i] = v[i + 1] - v[i];
}
sort(diff.begin(), diff.end());
int ans = min(k - 1, n);
for(int i = 0; i < n - k; i++){
ans += diff[i];
}
ans++;
cout << ans << '\n';
}
/*
10 5
1
2
5
6
8
11
13
15
16
20
1 3
5 7
8 9
11 12
13 14
15 20
*/
/*
freopen("x.in", "r", stdin);
freopen("x.out", "w", stdout);
*/
//atilla
