#include <bits/stdc++.h>
//#pragma GCC optimize("O3")
#define fi first
#define se second
#define pb push_back
#define ll long long
#define lf (id<<1)
#define rg (id<<1)|1
//#define mid ((l+r)>>1)
#define int long long
using namespace std;
typedef pair<int,int> pii;
typedef pair<pii, int> ipii;
const int MAXN = 2e5+10;
const int MAXA = 1e6+10;
const int SQRT = 700;
const int MOD = 998244353;
const int LOG = 31;
const int PRIME = 62;
int n, k;
int a[MAXN];
vector <int> dif;
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> k;
for(int i=1; i<=n; i++) cin >> a[i];
if(n==1){ cout << "1\n"; exit(0); }
for(int i=2; i<=n; i++) if(a[i]-a[i-1]-1 != 0) dif.pb(a[i]-a[i-1]-1);
sort(dif.rbegin(), dif.rend());
int ans = a[n]-a[1]+1;
for(int i=0; i<min(k-1, (int)dif.size()); i++) ans -= dif[i];
cout << ans << '\n';
}
