#include<bits/stdc++.h>
using namespace std;
#define f first
#define s second
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, k; cin >> n >> k;
int a[n]; for(int i = 0; i < n; ++i) cin >> a[i];
sort(a, a + n);
int s = a[n - 1] - a[0] + 1;
vector<pair<int, int>> b;
for(int i = 1; i < n; ++i)
b.push_back({a[i - 1] + 1, a[i] - 1});
sort(b.begin(), b.end(), [](const auto &a, const auto &b) {
return (a.s - a.f) > (b.s - b.f);
});
for(int i = 0; i < min(k - 1, n - 1); ++i) {
if(b[i].f > b[i].s) break;
s -= b[i].s - b[i].f + 1;
}
cout << s;
}
