//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define ll long long
#define ii pair<int, int>
#define vi vector<int>
#define vll vector<ll>
#define vii vector<ii>
#define cd complex<double>
#define ld long double
#define all(x) (x).begin(), (x).end()
#define iii tuple<int, int, int>
const ll mod = 1e9 + 7;
const ll INF = 1e18L + 5;
const double PI = acos(-1);
const int block = 320;
const int N = 2e5;
int tc, tt = 1;
int n, k;
vll f;
void solve() {
cin>>n>>k;
f.resize(n);
for(int i=0; i<n; i++) cin>>f[i];
vll g;
for(int i=1; i<(int)f.size(); i++) g.pb(f[i] - f[i - 1] - 1);
sort(g.begin(), g.end(), greater<ll>());
ll ans = (int)f.size();
for(int i=1; i<=n-k; i++) {
ans += g.back();
g.pop_back();
}
cout<<ans;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
for(tc=1; tc<=tt; tc++) solve();
cerr<<"\nTime elapsed: "<<1000.0*clock()/CLOCKS_PER_SEC<<" ms.\n";
return 0;
}
