#include <iostream>
#include <math.h>
#include <vector>
#include <string>
#include <algorithm>
#include <queue>
#include <stack>
#include <map>
#include <cstring>
#include <iomanip>
#include <stdio.h>
#include <unordered_map>
#include <bitset>
#include <tuple>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using piii = tuple<int,int,int>;
#define endl '\n'
#define f first
#define s second
int main(){
int n;cin >> n;
int m;cin >> m;
vector<int> vc;
int last;
cin >> last;
for(int i{};i < n-1;i++){
int g;cin >> g;
vc.emplace_back(g-last-1);
last = g;
}
vc.emplace_back(1);
sort(vc.begin(),vc.end());
int ans = n;
for(int i = 0;i < n-m;i++){
ans += vc[i];
}
cout << ans;
}
