#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define ull unsigned long long
#define pb push_back
#define fi first
#define sc second
#define vi vector<int>
#define pii pair<int,int>
#define vpi vector<pair<int,int> >
#define mp make_pair
const ll MOD1 = 1e9+7;
const ll MOD2 = 998244353;
const ll MOD3 = 1e9+93;
const ll MOD4 = 1e9+97;
const ll p1 = 1e9+87;
const ll p2 = 1e9+9;
const int INF = 1e9+7;
const int BASE = 1<<20;
const int LOG = 20;
const int ALF = 27;
const int MAXN = 1e6+7;
const int MAXNN = 1e3+7;
int t[MAXN];
vi diff;
void solve(){
int n,k; ll res;
cin>>n>>k;
for(int i=1;i<=n;i++) cin>>t[i];
res=t[n]+1-t[1];
for(int i=2;i<=n;i++) diff.pb(t[i]-t[i-1]-1);
sort(diff.begin(),diff.end()), reverse(diff.begin(),diff.end());
for(int i=0;i<k-1;i++) res-=diff[i];
cout<<res<<'\n';
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int tt=1;
while(tt--) solve();
return 0;
}
