#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define fi first
#define se second
#define ll long long
#define pii pair<int,int>
#define piii pair<int, pair<int, int>
#define v(int) vector<int>
#define si size()
#define foe(i,a,b) for(int i=a;i<=b;++i)
#define fol(i,a,b) for(int i=a;i<b;++i)
#define pb push_back
#define Bit(mask,i) (1<<i)&mask
#define offBit(mask,i) (1<<i)^mask
#define onBit(mask,i) (1<<i)mask
#define CNT(x) __builtin_popcountll(x)
const ll int mod = 1e9+7;
const ll int base = 2309;
const ll int inf = 1e18;
const int N = 1e6+10;
const int LG = 20;
// ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄▄ ▄ ▄▄▄▄
// █▄▄█ █ █ █ █ █▄▄█ █ █ ██ █ █ ▄▄
// █ █ █▄▄█ █▄▄█ █ █ █▄▄█ █ ██ █▄▄█
ll n, k;
priority_queue<int, v(int), greater<int>> pq;
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
int last;
cin >> last;
fol(i,1,n)
{
int t;
cin >> t;
pq.push(t - last - 1);
last = t;
}
int ans = n;
fol(i,0,n-k)
{
ans += pq.top();
pq.pop();
}
cout << ans;
}
