#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define endl '\n'
#define fi first
#define se second
#define For(i, l, r) for (int i = l; i < r; i++)
#define ForE(i, l, r) for (int i = l; i <= r; i++)
#define FordE(i, l, r) for (int i = l; i >= r; i--)
#define Fora(v, a) for (auto v: a)
#define bend(a) a.begin(), a.end()
#define isz(a) ((signed)a.size())
typedef long long ll;
typedef long double ld;
typedef pair <int, int> pii;
typedef vector <int> vi;
typedef vector <pii> vpii;
typedef vector <vi> vvi;
const int N = 1e5 + 5;
int n, k;
int t[N];
priority_queue <int, vi, greater <int>> pq;
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// freopen("stove.inp", "r", stdin);
// freopen("stove.out", "w", stdout);
cin >> n >> k;
ForE(i, 1, n){
cin >> t[i];
}
ForE(i, 2, n){
pq.push(t[i] - t[i - 1] - 1);
}
int ans = n;
ForE(i, 1, n - k){
ans += pq.top(); pq.pop();
}
cout << ans << endl;
}
/*
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INPUT: |
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OUTPUT: |
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*/
