#include<bits/stdc++.h>
#define ll long long
#define pb push_back
#define mp make_pair
#define ull unsigned long long
#define PI 3.141592653589793238
using namespace std;
ll binpow (ll a, ll b){
if (b == 0) return 1;
if (b & 1) return binpow(a, b - 1) * a;
else return binpow(a, b / 2) * binpow(a, b / 2);
}
ll gcd(ll a, ll b){
return (b ? gcd(b, a % b) : a);
}
ll nums(ll g){
ll cur = 0;
while(g){
cur++, g /= 10;
}
return cur;
}
bool comp(vector <pair <ll, ll> > a, vector <pair <ll, ll> > b){
return a.size() < b.size();
}
ll get1(ll q, ll g){
ll cur = 1;
for (ll i = q; i > g; i--){
cur *= i;
}
return cur;
}
const ll mod = (ll)998244353;
ll n, k, t = 1, a[200005], p[200005];
vector <ll> v;
string s;
ll dp[500][500];
int main(){
ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
//freopen("success.in", "r", stdin);
//freopen("success.out", "w", stdout);
cin >> n >> k;
ll mn = (ll)1e15, mx = 0;
for (ll i = 1; i <= n; i++){
cin >> a[i];
if (i > 1) v.pb(abs(a[i] - a[i - 1]));
mn = min(mn, a[i]);
mx = max(mx, a[i]);
}
ll ans = mx - mn + 1;
sort (v.begin(), v.end());
ll cur = v.size() - 1;
while(cur >= 0 && k > 1){
ans -= (v[cur] - 1);
cur--;
k--;
}
cout << ans;
return 0;
}
/**
4 16
10100
20
00101
10100
24
*/
