#include "bits/stdc++.h"
using namespace std;
#define int long long
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define ff first
#define ss second
#define pb push_back
template<class T, class U> inline bool chmin(T& a, const U& b) { if (a > b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmax(T& a, const U& b) { if (a < b) { a = b; return true; } return false; }
const int inf = 2e18;
const int mod = 1e9 + 7;
const int N = 2e5 + 1;
void solve(){
int n,k;
cin >> n >> k;
int t[n];
for(int i = 0;i < n;i++) {
cin >> t[i];
}
//~ int ans = 0;
vector<int> v;
for(int i = 0;i < n - 1;i++) {
v.pb(t[i + 1] - t[i] - 1);
}
sort(all(v));
int ans = n;
for(int i = 0;i < n - k;i++) {
ans += v[i];
}
cout << ans << "\n";
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
int T = 1;
//~ cin >> T;
while(T--) {
solve();
}
}
