//Huyduocdithitp
#include <bits/stdc++.h>
typedef long long ll;
#define endl '\n'
#define yes cout<<"YES"<<endl;
#define no cout<<"NO"<<endl;
#define fi first
#define se second
#define pii pair<ll, ll>
#define inf 1e18
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define MP make_pair
#define TASK "ghuy4g"
#define start if(fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin);freopen(TASK".out","w",stdout);}
#define LOG 19
#define N 500005
using namespace std;
ll n, k;
ll a[N], b[N], f[N];
signed main(void) {
faster;
cin >> n >> k;
for (int i = 1; i <= n; i ++) {
cin >> a[i];
f[i] = a[i] - a[i - 1] - 1;
}
sort(f + 2, f + 1 + n);
ll ans = n;
ll left = n - k;
for (int i = 2; i <= 2 + left - 1; i ++) {
ans += f[i];
}
cout << ans;
return 0;
}
