#include<bits/stdc++.h>
using namespace std;
#define ioss ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define int long long
#define tup tuple<int, int, int>
#define pii pair<int, int>
#define fi first
#define se second
#define pub push_back
#define pob pop_back
int n, k;
signed main() {
ioss;
cin >> n >> k;
int t[n+2] = {};
vector<int> diff;
for(int i = 1; i <= n; i++) cin >> t[i];
int ans = t[n]-t[1];
for(int i = 2; i <= n; i++) diff.pub(t[i]-t[i-1]);
sort(diff.rbegin(), diff.rend());
for(int i = 0; i < k-1; i++) ans -= diff[i];
ans += k;
cout << ans << endl;
}
