#include <bits/stdc++.h>
using namespace std;
#define int ll
typedef long long ll;
typedef pair<int,int> pi;
typedef vector <ll> vi;
typedef vector <pi> vpi;
typedef pair<pi, ll> pii;
typedef set <ll> si;
typedef long double ld;
#define f first
#define s second
#define mp make_pair
#define FOR(i,s,e) for(int i=s;i<=int(e);++i)
#define DEC(i,s,e) for(int i=s;i>=int(e);--i)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define lbd(x, y) lower_bound(all(x), y)
#define ubd(x, y) upper_bound(all(x), y)
#define aFOR(i,x) for (auto i: x)
#define mem(x,i) memset(x,i,sizeof x)
#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define MOD 1000000007
#define maxn 100001
//~ #define getchar_unlocked _getchar_nolock
int N,K,T[maxn];
int32_t main() {
fast;
cin >> N >> K;
FOR(i,1,N) cin >> T[i];
vi ranges;
FOR(i,1,N-1) ranges.pb(T[i+1] - T[i] - 1);
int ans = N;
sort(all(ranges));
FOR(i,0,N-K-1) ans += ranges[i];
cout << ans;
}
