#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
void debug_out() { cerr << endl; }
template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
cerr << "[" << H << "]";
debug_out(T...);
}
#ifdef dddxxz
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
#define SZ(s) ((int)s.size())
#define all(x) (x).begin(), (x).end()
#define revall(x) (x).rbegin(), (x).rend()
clock_t startTime;
double getCurrentTime() {
return (double) (clock() - startTime) / CLOCKS_PER_SEC;
}
typedef long long ll;
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
const double eps = 0.00001;
const int MOD = 1e9 + 7;
const int INF = 1000000101;
const long long LLINF = 1223372000000000555;
const int N = 1e6 + 3e2;
const int M = 2222;
int a[N];
void solve(int TC) {
int n, k;
cin >> n >> k;
vector<int> v;
for (int i = 1; i <= n; i++){
cin >> a[i];
if (i > 1) v.push_back(a[i] - a[i - 1]);
}
int ans = a[n] - a[1] + 1;
sort(revall(v));
for (int i = 0; i < min(SZ(v), k - 1); i++){
ans -= v[i] - 1;
}
cout << ans;
}
int main() {
startTime = clock();
cin.tie(nullptr); cout.tie(nullptr);
ios_base::sync_with_stdio(false);
bool llololcal = false;
#ifdef dddxxz
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
llololcal = true;
#endif
int TC = 1;
// cin >> TC;
for (int test = 1; test <= TC; test++) {
//debug(test);
//cout << "Case #" << test << ": ";
solve(test);
}
if (llololcal) cerr << endl << "Time: " << int(getCurrentTime() * 1000) << " ms" << endl;
return 0;
}
