#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL);
ll n, k; cin >> n >> k;
priority_queue<pair<ll, pair<ll, ll>>> pq;
ll arr[n + 5];
for (ll i = 1; i <= n; i++) cin >> arr[i];
for (ll i = 2; i <= n; i++){
pq.push({arr[i] - arr[i - 1], {i, i - 1}});
}
ll sisa = k - 1;
set<pair<ll, ll>> st;
while(sisa--){
auto ptr = pq.top(); pq.pop();
ll idx0 = ptr.second.second, idx1 = ptr.second.first;
st.insert({idx0, idx1});
}
ll ans = 0, l = 1;
for (ll i = 1; i <= n; i++){
if (st.find({i, i + 1}) != st.end() || i == n){ //ada
ans += (arr[i] - arr[l]) + 1;
l = i + 1;
}
}
cout << ans << endl;
}
/*
*/
