/*
Author: ArifKraw
Rating: 1379
Goal#1: Beat I_Love_Trott ))))
Goal#2: Not to allow FractalFrog beat myself
*/
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define pf push_front
#define ppf pop_front
#define ppb pop_back
#define mp make_pair
#define ff first
#define ss second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define ll long long
#define ld long double
#define nl '\n'
const ll N = 1e5 + 7;
const ll mod = 1e9 + 7;
const ll inf = 1e18;
const ld pi = 3.141592653589793;
const ld eps = 1e-12;
const ll zero = 0;
const int MAX = 1e6+5;
const int A = 1e9 + 5;
/*if you cant solve the problem:
try optimized(clever) brute-force;
try prefix sums with/or binary search
try dp
try dfs
try to solve in reversed orderr
try math
try to sort(sort(a+1,a+1+n)
int overflow, array bounds
think about special cases( n=1?)
*/
ll xx1[8]={0, 0,-1, 1, 1,-1, 1,-1};
ll xx2[8]={1,-1, 0, 0, 1, 1,-1,-1};
ll a[N],val[N];
void egoist(){
ll n,k;
cin>>n>>k;
for(int i=1;i<=n;i++){
cin>>a[i];
}
for(int i=2;i<=n;i++){
val[i-1]=a[i]-a[i-1];
}
n--;
ll ans=0;
sort(val+1,val+n+1);
for(int i=1;i<=n+1-k;i++){
ans+=val[i];
}
cout<<ans+k<<nl;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
//freopen("sparse.in", "r", stdin);
//freopen("sparse.out", "w", stdout);
egoist();
}
