#include <time.h>
#include <cstdlib>
#include <stack>
#include <numeric>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <map>
#include <set>
#include <iterator>
#include <deque>
#include <queue>
#include <sstream>
#include <array>
#include <string>
#include <tuple>
#include <chrono>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <list>
#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <bitset>
#define ll long long
using namespace std;
int tt = 1, n, k;
ll a[100005], sum;
vector<int> v;
int main(){
ios::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
cin >> n >> k;
for(int i = 1; i <= n; i++){
cin >> a[i];
if(i > 1) v.push_back(a[i] - a[i - 1]);
}
sum = a[n] - a[1] + 1;
sort(v.begin(), v.end());
while(k > 1){
k--;
sum = sum - v.back() + 1;
v.pop_back();
}
cout << sum;
}
