#include <bits/stdc++.h>
#define fst first
#define snd second
#define ll long long
#define ld long double
#define pb push_back
#define emp emplace_back
#define pii pair<int, int>
#define usg unsigned
#define sg signed
#define mp make_pair
using namespace std;
void setIO(){
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
}
const ld PI = 4*atan((ld)1);
const int INF = 1e9+7;
const ll _INF = 1e18+7;
vector<int>v, vs;
int main(){
setIO();
int n, k;
cin >> n >> k;
for (int i = 0; i < n; i++){
int x; cin >> x;
v.emp(x);
}
for (int i = 1; i < n; i++)
vs.emp(v[i]-v[i-1]);
sort(vs.begin(), vs.end(), greater<int>());
ll sum = 0;
for (int i = 0; i < k-1; i++)
sum += vs[i];
cout << v[n-1]-v[0]+k-sum << endl;
}
