#include <bits/stdc++.h>
#define endl '\n'
#define fr first
#define sc second
#define all(v) v.begin(),v.end()
#define unq(v) sort( all(v) ); v.erase( unique( all(v) ), v.end() )
#define bout(x) cout << bitset<sizeof(x)*8>(x) << endl
#define mkp(a,b) make_pair(a,b)
#define gcd(a,b) __gcd(a,b)
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using cpl = complex<ld>;
const ld pi = 3.14159265358979323846264338327950288;
const ld tau = 2 * pi;
const int dx[4] = {0, 1, 0, -1}, dy[4] = {-1, 0, 1, 0};
const int ddx[8] = {0, 1, 1, 1, 0, -1, -1, -1}, ddy[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
const int nx[8] = {1, 2, 2, 1, -1, -2, -2, -1}, ny[8] = {-2, -1, 1, 2, 2, 1, -1, -2};
//#define DEBUG
ll arr[100020];
priority_queue<pll, vector<pll>, greater<pll> > pq;
void Main(){
int n, k; cin >> n >> k;
for (int i = 1; i <= n; i++){
cin >> arr[i];
}
for (int i = 1; i < n; i++){
pq.push({ arr[i+1] - arr[i], i });
}
int cnt = n;
ll ans = n;
while (cnt > k){
ll dif = pq.top().fr, idx = pq.top().sc; pq.pop();
ans += dif-1; cnt -= 1;
}
cout << ans;
}
int main(){
#ifndef DEBUG
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
#endif
cout.setf(ios::fixed);
cout.precision(0);
Main();
}
