#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U>
void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T>
void debug(T L, T R) { while (L != R) cerr << *L << " \n"[next(L) == R], ++L; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 300010;
int n, k, t[MAX_N];
int32_t main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n >> k;
for (int i = 1;i <= n;++i)
cin >> t[i];
int res = t[n] - t[1] + 1;
vector<int> save(n-1);
for (int i = 1;i < n;++i)
save[i-1] = t[i+1] - t[i] - 1;
sort(AI(save), greater<>());
for (int i = 0;i + 1 < k;++i)
res -= save[i];
cout << res << '\n';
}
