#include<bits/stdc++.h>
#define f first
#define s second
using namespace std;
const int N = 2e5 + 500;
typedef pair<int , int> ipair;
int n , k;
int a[N];
vector<ipair> deltas;
set<int> s;
int main (){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> k;
for(int i = 0; i < n; ++i){
cin >> a[i];
if(i) deltas.emplace_back(a[i] - a[i - 1] , i - 1);
}
sort(deltas.begin() , deltas.end()); reverse(deltas.begin() , deltas.end());
for(int i = 0; i < k - 1; ++i){
s.insert(deltas[i].s);
//cerr << deltas[i].s << " ";
} //cerr << endl;
long long sum = 0;
int cur = 0;
for(int x : s){
//cerr << x << " x " << "cur " << cur << endl;
sum += (a[x] + 1 - a[cur]);
//cerr << a[x] << " a[x] " << " acur " << a[cur] << endl;
//cerr << sum << " sum " << endl;
cur = x + 1;
} sum += (a[n - 1] + 1 - a[cur]);
cout << sum << endl;
return 0;
}
