#pragma GCC optimize("O3")
#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 int long long
#define double long double
#define pii pair<int, int>
#define pb push_back
#define F first
#define S second
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define debug(x) cout << #x << " = " << x << '\n';
#define vdebug(a) cout << #a << " = "; for(auto x : a) cout << x << " "; cout << '\n';
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;
typedef tree<pii, null_type, less<pii>, rb_tree_tag, tree_order_statistics_node_update> indexed_pair_set;
const double eps = 1e-9;
const int mod = 1e9 + 7;
const int N = 2e5 + 5;
const int INF = 1e18;
void solve(){
int n, k; cin >> n >> k;
vector<int> v(n);
for(int i = 0; i < n; i++) cin >> v[i];
vector<int> x;
for(int i = 0; i < n - 1; i++) x.pb(v[i + 1] - (v[i] + 1));
sort(x.begin(), x.end());
int ans = n + accumulate(x.begin(), x.begin() + max(0LL, n - k), 0);
cout << ans << '\n';
}
signed main(){
fastio;
solve();
}
/*
freopen("x.in", "r", stdin);
freopen("x.out", "w", stdout);
*/
//atilla
