#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb push_back
#define mkp make_pair
#define ff first
#define ss second
#define all(a) a.begin(), a.end()
#define sz(a) (int)(a.size())
#define clr(a, b) memset(a, b, sizeof(a))
#define REP(i, a, b) for(int i=(int)(a); i<(int)(b); ++i)
#define REPD(i, a, b) for(int i=(int)(a)-1; i>=(int)(b); --i)
#define FOR(it,c) for ( __typeof((c).begin()) it=(c).begin(); it!=(c).end(); it++ )
template<typename T> inline bool chkmin(T &a, const T &b) { return a > b ? a = b, 1 : 0; }
template<typename T> inline bool chkmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int N = 100005;
ll a[N];
int n, kk;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> kk;
ll res = 0;
REP(i, 0, n) {
cin >> a[i];
}
res = a[n-1] - a[0] + 1;
vector<ll> v;
REP(i, 1, n) {
v.pb(a[i] - a[i-1] - 1);
}
sort(all(v));
reverse(all(v));
REP(i, 0, kk-1) {
res -= v[i];
}
cout << res << "\n";
return 0;
}
