#include <bits/stdc++.h>
using namespace std;
#define ios ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin() + 1, (x).rend()
#define fi first
#define se second
#define yes cout << "YES" << '\n'
#define no cout << "NO" << '\n'
#define int long long
#define veci vector<int>
#define skip continue
#define sz size()
#define pii pair<int,int>
const int mod = 1e9 + 7;
const int N = 2e6 + 7;
const int inf = 1e18;
void zertinii() {
int n, m;
cin >> n >> m;
veci a(n + 1);
for(int i = 1;i <= n;i++) {
cin >> a[i];
}
veci b;
for(int i = 1;i < n;i++) {
int kol = (a[i + 1] - a[i] - 1);
b.pb(kol);
}
sort(all(b));
int sum = 0;
for(int i = 0;i < n - m;i++) {
sum += b[i];
}
cout << n + sum;
}
signed main() {
ios;
int t = 1;
//cin >> t;
while(t--) {
zertinii();
}
return 0;
}
