#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = a; i<=b; i++)
#define FORD(i,a,b) for(int i = a; i>=b; i--)
#define vi vector<int>
#define vll vector<long long>
#define pb push_back
/*
Author: DreamNguyen aka Nguyen Minh Triet
*/
using namespace std;
using ll = long long;
const int maxN = 1e5;
int n, k;
ll t[maxN+5], que[maxN+5];
void nhap()
{
cin>>n>>k;
FOR(i,1,n) cin>>t[i];
}
void giai()
{
if(n==k) return void(cout<<n);
ll ans = t[n]-t[1]+1;
FOR(i,1,n-1) que[i] = t[i+1]-t[i]-1;
sort(que+1,que+n,greater<ll>());
FOR(i,1,k-1) ans -= que[i];
cout<<ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
nhap();
giai();
return 0;
}
