#include <bits/stdc++.h>
using namespace std;
//#define LOCAL
#define fi first
#define se second
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define ALL(v) (v).begin(), (v).end()
#define BIT(x) (1LL << (x))
#define MASK(x, i) (((x) >> (i)) & 1)
#define FOR(i, a, b) for(int i = (a), _b = (b); i <= _b; ++ i)
#define FORD(i, b, a) for(int i = (b), _a = (a); i >= _a; -- i)
const string NAME = "BAITAP";
const long long INF = 1e18;
const int inf = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const int mod = 998244353;
const int mxN = 1e5 + 5;
int N, K;
vector<int> d(mxN);
void init(void){
cin >> N >> K;
int a, b;
FOR(i, 1, N){
cin >> b;
if(i > 1) d[i - 1] = b - a - 1;
a = b;
}
}
void process(void){
sort(d.begin() + 1, d.begin() + N);
int ans = N;
FOR(i, 1, N - K) ans += d[i];
cout << ans;
}
signed main(void){
ios::sync_with_stdio(false);
cin.tie(nullptr);
#ifdef LOCAL
freopen((NAME + ".INP").c_str(), "r", stdin);
freopen((NAME + ".OUT").c_str(), "w", stdout);
#endif // I/O
init();
process();
cerr << "\nTime elapsed: " << TIME << "s.\n";
}
