#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define yes cout << "YES" << '\n';
#define no cout << "NO" << '\n';
#define sp " "
#define massiv(a , n) for (ll i = 0; i < n; i++) cin >> a[i];
#define pb push_back
#define ss second
#define ff first
// Code written by { >> Neguun << }
void neguun () {
ll n , k; cin >> n >> k;
vector < ll > t(n) , diff;
for (ll i = 0; i < n; i++) {
cin >> t[i];
if (i > 0) {
diff.pb(t[i] - t[i - 1]);
}
}
sort (diff.begin() , diff.end());
ll ans = n;
for (ll i = 0; i < n - k; i++) {
ans += diff[i] - 1;
}
cout << ans;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
ll test;
test = 1;
//cin >> test;
while (test--) {
neguun ();
}
return 0;
}
