#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef multiset<int> mi;
typedef vector<vector<int>> vvi;
typedef vector<vector<pair<int,int>>> vvpii;
typedef set<int> si;
const int INF = 1e9 + 7;
const ll LINF = 1e18 + 7;
const ll MOD = 1e9;
const double EPS = 1e-9;
const double PI = acos(-1.0);
#define fastio ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define F first
#define S second
int t;
inline void solve() {
int N, K;
cin >> N >> K;
vi g;
if(K >= N) {cout << N << '\n'; return;}
for(int i = 0;i<N;i++){
int t1; cin >> t1;
g.pb(t1);
}
int max = g[g.size()-1] - g[0];
vi v;
for(int i = g.size()-1; i>0;i--){
v.pb(g[i] - g[i-1]);
}
sort(all(v));
int res = 0;
int pos= 0;
while(N != K){
N--;
res += v[pos];
pos++;
}
cout << max-res;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
t = 1;
while(t--) solve();
return 0;
}
