#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int tt = 1;
//cin >> tt;
while(tt--) {
int n, k;
cin >> n >> k;
vector<int> a(n);
for(int i = 0;i < n;i++)
cin >> a[i];
vector<pair<int, int>> p(n);
for(int i = 1;i < n;i++)
p[i] = {a[i] - a[i - 1], i - 1};
sort(p.begin(), p.end(), greater<pair<int, int>>());
vector<int> g;
for(int i = 0;i < k - 1;i++)
g.push_back(p[i].s);
sort(g.begin(), g.end());
int ans = 0;
int ptr = a[0];
for(auto x : g) {
ans += a[x] + 1 - ptr;
ptr = a[x + 1];
}
ans += a[n - 1] + 1 - ptr;
cout << ans;
}
return 0;
}
