#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <vector>
using namespace std;
// BEGIN NO SAD
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
typedef vector<int> vi;
// END NO SAD
typedef long long ll;
typedef pair<int, int> pii;
int l[100005];
void solve() {
int n, k;
cin >> n >> k;
for(int i = 0; i < n; i++) cin >> l[i];
int ret = l[n-1] - l[0] + 1;
priority_queue<int> q;
for(int i = 1; i < n; i++) q.push(l[i] - l[i-1] - 1);
while(k-- > 1) {
ret -= q.top(); q.pop();
}
cout << ret << "\n";
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
solve();
}
