#include <bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " : " << x << '\n'
using namespace std;
typedef long long ll;
typedef long double ld;
typedef string str;
typedef pair<ll, ll> pll;
const ll Mod = 1000000007LL;
const int N = 2e5 + 10;
const ll Inf = 2242545357980376863LL;
const ll Log = 30;
vector<int> V;
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, k;
cin >> n >> k;
int nw, la;
cin >> la;
for(int i = 1; i < n; i++){
cin >> nw;
V.pb(nw - la - 1);
la = nw;
}
ll ans = n;
sort(all(V));
for(int i = 0; i < n - k; i++) ans += V[i];
cout << ans << '\n';
return 0;
}
