#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
#pragma GCC optimize ("O4")
#pragma GCC optimize ("fast-math")
#pragma GCC optimize ("unroll-loops")
using namespace std;
#define int long long
#define ll long long
#define XX first
#define YY second
#define pb push_back
#define sz (x) int(x.size())
#define pf pop_front
#define pob pop_back
#define pff push_front
signed main(void){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n, k;
cin >> n >> k;
if (k >= n){
cout << n;
return 0;
}
else{
vector <int> v;
int x, cp;
cin >> x;
cp = x;
int sum = n;
for (int i = 0; i < n - 1; ++ i){
cin >> x;
v.push_back(x - cp - 1);
cp = x;
}
sort (v.begin(), v.end());
for (int i = 0; i < n - k; ++ i){
sum += v[i];
}
cout << sum;
}
return 0 ^ 0;
}
