#include <bits/stdc++.h>
#define loop(i,a,b) for(int i = (a); i < (b); i ++)
#define pb push_back
#define ins insert
#define pii pair<int,int>
#define ff first
#define ss second
#define op(x) cerr << #x << " = " << x << endl;
#define opa(x) cerr << #x << " = " << x << ", ";
#define ops(x) cerr << x;
#define entr cerr << endl;
#define spac cerr << ' ';
#define STL(x) cerr << #x << " : "; for(auto &qwe:x) cerr << qwe << ' '; cerr << endl;
#define ARR(x, nnn) cerr << #x << " : "; loop(qwe,0,nnn) cerr << x[qwe] << ' '; cerr << endl;
#define BAE(x) x.begin(), x.end()
#define unilize(x) x.resize(unique(BAE(x)) - x.begin())
#define unisort(x) sort(BAE(x)); unilize(x);
using namespace std;
const int mxn = (int)(1e5) + 10;
int a[mxn];
int main(){
int n, k; cin >> n >> k;
int ans = n;
loop(i,0,n){
cin >> a[i];
}
vector<int> v;
loop(i,1,n){
v.pb(a[i] - a[i-1] - 1);
}
sort(BAE(v));
int take = n - k;
loop(i,0,take){
ans += v[i];
}
cout << ans;
}
