#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define pb push_back
#define F first
#define S second
#define endl "\n"
const int INF = 1e18+10;
const int MOD = 1e9+7;
int n, k;
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> k;
vector<int> v(n);
for(int i = 0; i < n; i++) {
cin >> v[i];
}
vector<int> dist(n-1);
for(int i = 1; i < n; i++) {
dist[i-1] = v[i] - v[i-1];
}
sort(dist.rbegin(), dist.rend());
int resp = v[n-1] + 1 - v[0];
k--;
int i = 0;
while(k) {
resp -= dist[i] - 1;
i++;
k--;
}
cout << resp << endl;
return 0;
}
