#include<bits/stdc++.h>
#define ll long long
using namespace std;
void setIO() {
cin.tie(0)->sync_with_stdio(0);
//ios_base::sync_with_stdio(false); cin.tie(0);
}
const int N = 1e6 + 10;
int t;
ll ans;
ll n,m,k;
ll a;
ll res;
int pos;
ll c;
ll b;
int no;
ll sum =0;
int main() {
setIO();
int t;
t=1;
while(t--){
cin >> n >> k;
ll a[n],b[n];
for(int i =0;i<n;++i){
cin >> a[i];
}
ll value = a[n-1]+1- a[0];
for(int i =0;i<n-1;++i){
b[i]= (a[i+1] - (a[i]+1));
}
sort(b,b+(ll)n-1);
for(int i =0;i<k-1;++i){
value -= b[n-2-i];
}
cout << value ;
}
}
