#include<bits/stdc++.h>
#define fi first
#define se second
#define ll long long
#define pii pair<int,int>
#define piii pair<int,pii>
int const ee = 1e9 + 7;
using namespace std;
int s[100005];priority_queue<int,vector<int>>pq;
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int n,m;cin>>n>>m;
int nn=INT_MAX,mm=INT_MIN;
for(int i=1;i<=n;i++){
cin>>s[i];
if(i>1)pq.push(s[i]-s[i-1]);
mm=max(mm,s[i]);nn=min(nn,s[i]);
}
int ss = mm-nn;int mmm = m;
m--;
while(m--){
//cout<<pq.top();
ss-=pq.top();pq.pop();
}
cout<<ss+mmm;
return 0;
}
