#include <bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
using namespace std;
template <class X, class Y> bool minimize(X &a, Y b) {
if (a > b) return a = b, true;
return false;
}
template <class X, class Y> bool maximize(X &a, Y b) {
if (a < b) return a = b, true;
return false;
}
signed main() {
cin.tie(0)->sync_with_stdio(0);
int n, k; cin >> n >> k;
vector<int> a(n + 1);
for (int i = 1; i <= n; i ++) {
cin >> a[i];
}
vector<int> gap;
long long res = a[n] - a[1] + 1;
for (int i = 2; i <= n; i ++) {
gap.push_back(a[i] - a[i - 1] - 1);
}
sort(gap.begin(), gap.end());
reverse(gap.begin(), gap.end());
k --;
for (int x: gap) {
if ((-- k) < 0) {
break;
}
res -= x;
}
cout << res;
return 0;
}
