#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define pb push_back
#define pii pair<int, int>
#define pll pair<ll, ll>
#define mll map<ll, ll>
#define fi first
#define se second
int n, k, t;
int a[200001], dif[200001];
int main() {
fastio;
cin >> n >> k;
cin >> a[1];
for (int i = 2; i <= n; i++) {
cin >> a[i];
dif[i] = a[i]-a[i-1];
}
t = a[n]-a[1]+1;
sort(dif+1, dif+n+1);
for (int i = n; (i >= 1 && k > 1); i--, k--) {
t -= (dif[i]-1);
}
cout << t << endl;
}
