rt

#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,m,a[15010],b[15010];
signed main(){
cin>>n>>m;
for(int i=1;i<=n;i++){
    cin>>a[i];
    b[i-1]=a[i]-a[i-1];
}
sort(b,b+n);
int sum=0;
for(int i=0;i<=n-m;i++){
    sum+=b[i];
    //cout<<sum<<" ";
}
cout<<sum+m;
return 0;
}