#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define ull unsigned long long
#define fi first
#define se second
#define ld long double
ll n, k, arr[100005];
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> k;
for(int i=1;i<=n;++i){
cin >> arr[i];
}
priority_queue<ll>pq;
for(int i=2;i<=n;++i){
pq.push((arr[i]-1)-(arr[i-1]+1)+1);
}
ll sums=arr[n]-arr[1]+1;
k--;
while(!pq.empty() && k){
sums-=pq.top();
pq.pop();
k--;
}
cout << sums << '\n';
}
