#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <algorithm>
#include <math.h>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
using namespace std;
ifstream in("input.txt");
ofstream out("output.txt");
typedef long long ll;
int n,k;
ll v[100001];
ll tot=0;
ll diff[100001];
bool cmp(int a, int b){
return a>b;
}
int main(){
cin>>n>>k;
v[0]=-1e9-1;
cin>>v[0];
for(int i=1;i<=n-1;i++){
cin>>v[i];
tot+=v[i]-v[i-1];
diff[i]=v[i]-v[i-1];
}
sort(diff+1,diff+n,cmp);
for(int i=1;i<=k-1;i++){
tot-=diff[i]-1;
}
//if(k>=2&&v[1]-v[0]<diff[k-1])tot+=1;
tot+=1;
cout<<tot;
}
