#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
const ll mod=1e9+7;
const ll maxn=1e5+5;
const int INF=1e9;
#define ok ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define fi first
#define se second
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define endl '\n'
int n, k, arr[maxn], ans;
priority_queue<int> pq;
int main() {
ok
cin >> n >> k;
for(int i=0; i<n; i++) {
cin >> arr[i];
}
ans=arr[n-1]-arr[0]+1;
for(int i=1; i<n; i++) {
pq.push(arr[i]-arr[i-1]-1);
}
while(!pq.empty()) {
if(k==1) break;
ans-=pq.top();
pq.pop();
k--;
}
cout << ans;
}
