//#pragma GCC optimize("O3")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
//#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int mod = 998244353;
ll binpow(ll a, ll p) {
ll res = 1;
while (p) {
if (p & 1) {
(res *= a) %= mod;
}
p >>= 1;
(a *= a) %= mod;
}
return res;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n, k;
cin >> n >> k;
vector<int> a(n);
vector<int> dif(n - 1);
for (int i = 0; i < n; i++) {
cin >> a[i];
if (i) {
dif[i - 1] = a[i] - a[i - 1] - 1;
}
}
int ans = n;
sort(dif.begin(), dif.end());
for (int i = 0; i < n - k; i++) {
ans += dif[i];
}
cout << ans;
return 0;
}
