/*
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("O3")
#pragma GCC target ("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
*/
#include<bits/stdc++.h>
#define sz(v) (int)v.size()
#define ll long long
#define pb push_back
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define nl "\n"
using namespace std;
using pii = pair<int, int>;
const int N = (int)1e5 + 7; // make sure this is right
const int M = (int)1e6 + 7;
const int inf = (int)1e9 + 7;
const ll INF = (ll)3e18 + 7;
const ll MOD = (ll)998244353; // make sure this is right
bool bit(int x, int i) {
return x >> i & 1;
}
pii dir[] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
int n, k, a[N];
void solve() {
cin >> n >> k;
for(int i = 1; i <= n; ++i) {
cin >> a[i];
}
int ans = a[n] - a[1];
vector<int> v;
for(int i = 2; i <= n; ++i) v.pb(a[i] - a[i - 1]);
sort(rall(v));
for(int i = 0; i < k - 1; ++i) ans -= v[i];
cout << ans + k;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
int test = 1;
//cin >> test;
for(int i = 1; i <= test; ++i) {
//cout << "Case #" << i << ": ";
solve();
}
return 0;
}
