#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int, int> pi;
#define debug(x) cerr << #x << ": " << x << endl;
#define debug2(x, y) debug(x) debug(y);
#define repn(i, a, b) for(int i = (int)(a); i < (int)(b); i++)
#define rep(i, a) for(int i = 0; i < (int)(a); i++)
#define all(v) v.begin(), v.end()
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define endl '\n'
template<class T> T gcd(T a, T b){ return ((b == 0) ? a : gcd(b, a % b)); }
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
//freopen("input.in", "r", stdin);
//freopen("output.out", "w", stdout);
int n, k;
cin >> n >> k;
vi t(n);
rep(i, n) cin >> t[i];
ll ans = n; //best case scenario
int cc = 0;
vi wait;
repn(i, 1, n){
if(!(t[i] == (t[i - 1] + 1))){
wait.pb(t[i] - t[i - 1] - 1);
cc++;
}
}
cc++;
sort(all(wait));
rep(i, max(0, cc - k)) ans += wait[i];
cout << ans << endl;
return 0;
}
/*
Things to look out for:
- Integer overflows
- Array bounds
- Special cases
Be careful!
*/
