#include <bits/stdc++.h>
#define ll long long int
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define SZ(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define MS(x,a) memset((x), (a), sizeof(x))
#define F0R(i,n) for(auto (i) = 0; (i) < (n); (i)++)
#define FOR(i,a,b) for(auto (i) = (a); (i) <= (b); (i)++)
#define ROF(i,a,b) for(auto (i) = (a); (i) >= (b); (i)--)
using namespace std;
const int INF = 1e9+2;
const ll LINF = 1e18+2;
const int MX = 2e5+5;
const ll MOD = 1e9+7;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int n,k; cin >> n >> k;
ll t[n]; F0R(i,n) cin >> t[i];
vector<ll> segs;
FOR(i,1,n-1) {
segs.pb(t[i]-t[i-1]-1);
}
sort(all(segs));
ll ans = n;
F0R(i,n-k) ans += segs[i];
cout << ans;
}
