#include <bits/stdc++.h>
using namespace std;
#define mp(a,b) make_pair(a,b)
#define mt make_tuple
#define ff first
#define setp setprecision(12)<<fixed
#define ss second
#define fori(v) for(int i=0; i<v; i++)
#define forj(v) for(int j=0; j<v; j++)
#define fork(v) for(int k=0; k<v; k++)
#define forl(v) for(int l=0; l<v; l++)
#define fort(v) for(int t=0; t<v; t++)
#define forz(v) for(int z=0; z<v; z++)
#define ll long long
#define lll __int128
#define ld long double
#define pb(a) push_back(a)
// #define cout out
// #define cin in
ll inf = pow(10,18);
ll modulo = 1000000007;
double eps = 1e-10;
ifstream in;
ofstream out;
void deal(){
ll n, k;
cin>>n>>k;
vector<ll> arr(n);
fori(n){
cin>>arr[i];
}
vector<ll> all;
for(ll i = 0; i<n-1; i++){
all.pb(arr[i] + 1 - arr[i+1]);
}
sort(all.begin(), all.end());
ll ans = arr[n-1] + 1 - arr[0];
fori(k-1){
ans += all[i];
}
cout<<ans;
}
int main(){
cin.tie(0);
ios_base::sync_with_stdio(0);
deal();
}
