#include <bits/stdc++.h>
using namespace std;
#define nl '\n'
using ll = long long;
#ifdef LOCAL
#include "algo/debug.h"
#else
#define dbg(...)
#endif
void solve() {
int N, K;
cin >> N >> K;
vector<int> T(N);
for (int i = 0; i < N; ++i) { cin >> T[i]; }
int ans = T[N - 1] - T[0] + 1;
priority_queue<int> PQ;
for (int i = 1; i < N; ++i) { PQ.push(T[i] - T[i - 1]); }
while (K-- > 1) {
auto len = PQ.top();
PQ.pop();
ans -= len - 1;
dbg(len, ans);
}
cout << ans << nl;
}
signed main() {
std::ios_base::sync_with_stdio(0), std::cin.tie(0);
solve();
}
