#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define int int_fast32_t
#define ul uint_fast32_t
#define ll int_fast64_t
#define dll long double
#define ull uint_fast64_t
#define spektar this_thread::sleep_for(chrono::milliseconds(50))
void solve(){
int n,m;
cin >> n >> m;
vector<int> k(n);
vector<int> kk;
int m1=m;
for(auto& i:k) cin >> i;
for(int i=1; i<n; i++) kk.push_back(k[i]-k[i-1]);
sort(k.begin(),k.end());
sort(kk.begin(),kk.end());
int s=0;
for(int i=n-2; i>=0 && m1-1>0; i--){
s+=kk[i];
m1--;
}
cout << k[n-1]-k[0]+m-s << endl;
}
signed main(){
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int t=1;
//cin >> t;
while(t--){
solve();
}
}
