#include<bits/stdc++.h>
using namespace std;
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define dbg(x) cout << #x << '=' << x << '\n';
#define ll long long
#define sz size()
#define x first
#define y second
#define pi pair <int, int>
#define pii pair <int, pi>
#define vi vector <int>
const ll mod = 1e9 + 7;
int n, k, t[100005];
vector <int> dif;
int32_t main(){
ios_base :: sync_with_stdio(0); cin.tie(); cout.tie();
cin>>n>>k;
for(int i=1; i<=n; i++) cin>>t[i];
for(int i=1; i<n; i++) dif.pb(t[i+1]-t[i]);
sort(dif.begin(), dif.end(), greater<int>());
int ans=0;
for(int i=1; i<k; i++) ans+=dif[i-1];
//cout<<ans;
cout<<t[n]-t[1]+k-ans;
}
