# include <bits/stdc++.h>
# define speed ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
# define int long long
using namespace std;
const int N = 2e3 + 7;
int32_t main() {
speed;
int n, k;
cin >> n >> k;
vector < int > t(n), use(n);
vector < pair < int, int > > vc;
for ( int i = 0; i < n; i++ ) {
cin >> t[i];
}
for ( int i = 1; i < n; i++ ) {
vc.push_back( { t[i] - t[i - 1], i } );
}
sort( vc.rbegin(), vc.rend() );
for ( int i = 0; i < k - 1; i++ ) {
use[ vc[i].second ] = 1;
}
int p = t[0], ans = 0;
for ( int i = 0; i < n; i++ ) {
if ( use[i] ) {
ans += (t[i - 1] + 1) - p;
p = t[i];
}
}
ans += (t[n - 1] + 1) - p;
cout << ans;
}
