#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define xx first
#define yy second
#define srt(a) sort(a.begin(),a.end());
#define srtg(a,int) sort(a.begin(),a.end(),greater<int>())
#define lb(a,x) lower_bound(a.begin(),a.end(),x)
#define up(a,x) upper_bound(a.begin(),a.end(),x)
#define fnd(a,x) find(a.begin(),a.end(),x)
#define vstart auto startt=chrono::system_clock::now()
#define vend auto endd=chrono::system_clock::now()
#define vvreme chrono::duration<double> vremee=endd-startt
#define ios ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef string str;
const int maxn=1e5+10;
int niz[maxn];
void solve(){
int n,k;
cin>>n>>k;
int prosli=0;
int res=1;
int koliko=0;
for(int i=0;i<n;i++){
int a;
cin>>a;
if(i!=0){
res+=a-prosli;
niz[koliko++]=a-prosli;
}
prosli=a;
}
sort(niz,niz+koliko,greater<int>());
for(int i=0;i<min(koliko,k-1);i++) res-=niz[i]-1;
cout<<res;
}
int main(){
ios;
int t=1;
//cin>>t;
while(t--) solve();
return 0;
}
