#include <bits/stdc++.h>
#define F first
#define S second
#define ll long long
#define pb push_back
#define endl '\n'
using namespace std;
const int MOD = 1e9 + 7;
const int N = 1e5 + 10;
int t[N];
bool e(pair<int,pair<int,int>> a, pair<int,pair<int,int>> b) {
return (a.S.F < b.S.S);
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n, k;
cin >> n >> k;
vector<pair<int, pair<int, int>>> v;
for (int i = 0; i < n; ++i) {
cin >> t[i];
if (i) v.pb({t[i] - t[i - 1], { i-1, i}});
}
sort(v.rbegin(), v.rend());
v.erase(v.begin() + k - 1, v.begin() + (v.size()));
sort(v.begin(), v.end(), e);
ll sum = 0;
int l = 0;
for ( auto i: v) {
//cout << i.S.F << " " << i.S.S << endl;
sum += (t[i.S.F] - t[l] + 1) * 1LL;
l = i.S.S;
}
sum += (t[n-1] - t[l] + 1) * 1LL;
cout << sum << endl;
}
