#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
typedef long long ll;
const ll INF = 1e18;
const ll MOD = 1e9 + 7;
const ll MAXN = 1e6 + 5;
const ll LOG = 30;
#define vll vector <ll>
#define pll pair <ll, ll>
#define fi first
#define se second
#define endl '\n'
#define debug(x) cout << #x << " " << (x) << endl;
ll n, m;
ll a [MAXN];
ll par [MAXN];
ll bpk(ll x){
if(par[x] == x) return x;
return par[x] = bpk(par[x]);
}
void mrg(ll x, ll y){
par[bpk(y)] = bpk(x);
}
void solve(){
cin >> n >> m;
for(ll i = 1; i <= n; i++){
cin >> a[i];
par[i] = i;
}
vector <pll> v;
for(ll i = 1; i < n; i++){
v.push_back({(a[i+1]-a[i]), i});
}
sort(v.begin(), v.end());
for(ll i = 0; i < n-m; i++){
mrg(v[i].se, v[i].se+1);
}
ll ans = 0;
ll las = 0;
for(ll i = 1; i <= n; i++){
if(bpk(i) == i){
if(las) ans += a[i-1] + 1 - a[las];
las = i;
}
}
ans += a[n] + 1 - a[las];
cout << ans << endl;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// ll t; cin >> t;
// while(t--) solve();
solve();
}
