#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#define fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file(s) freopen(s".in", "r", stdin);freopen(s".out", "w", stdout);
#define nano chrono::steady_clock::now().time_since_epoch().count()
#define uid uniform_int_distribution<int>
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define pb push_back
#define sz() size()
#define ft first
#define sd second
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef unsigned long long ull;
const int N = 1e5 + 10;
const int M = 1e7 + 5;
const ll inf = 1e15;
ll mod = 1e9 + 7;
const double Pi = acos(-1);
ll binpow(ll x, ll ti) { ll res = 1;while (ti){if(ti & 1)res *= x;x *= x;ti >>= 1; x %= mod; res %= mod;} return res;}
ll binmul(ll x, ll ti) { ll res = 0;while (ti){if(ti & 1)res += x;x += x;ti >>= 1; x %= mod; res %= mod;} return res;}
ll random(ll l, ll r) { mt19937 rnd(nano); uid dist(l, r); return dist(rnd); }
ll nok(ll a, ll b) { return (a*b)/__gcd(abs(a),abs(b)) * (a*b > 0 ? 1 : -1); }
bool odd(ll n) { return (n % 2 == 1); }
bool even(ll n) { return (n % 2 == 0); }
ll n, k, a[N];
const void solve(/*Armashka*/) {
cin >> n >> k;
for (int i = 1; i <= n; ++ i) cin >> a[i];
vector <ll> v;
for (int i = 1; i < n; ++ i) v.pb(a[i + 1] - a[i]);
sort(rall(v));
ll ans = 0;
for (int i = k - 1; i < v.sz(); ++ i) ans += v[i];
cout << ans + k;
}
signed main() {
srand(time(NULL));
fast;
// file("");
int tt = 1;
// cin >> tt;
for (int i = 1; i <= tt; ++ i) {
solve();
}
}
// Jelbiretip kok tudy, boys in the hood
// Kim qandai juz, kimde qandai ru
