#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define ff first
#define ss second
#define all(a) (a).begin(), (a).end()
template<typename T>
int len(T &a){
return a.size();
}
void solve(){
int n, k; cin >> n >> k;
vector<int> a(n);
for(auto &u : a){
cin >> u;
}
int ans = a.back() - a[0] + 1;
vector<int> dif;
for(int i = 1; i < n; i ++){
dif.push_back(a[i] - a[i - 1] - 1);
}
sort(all(dif), greater{});
//for(auto u : dif) cout << u << ' ';
for(int i = 0; i < k - 1; i ++){
ans -= dif[i];
}
cout << ans;
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
int testcases = 1;
#ifdef Tests
cin >> testcases;
#endif
while(testcases --){
solve();
if(testcases) cout << '\n';
#ifdef LOCAL
else
cout << '\n';
cout << "________________________" << endl;
#endif
}
#ifdef LOCAL
cout << "done" << endl;
#endif
return 0;
}
